|San Juan Capistrano
Weatherunderground current temperature
Typically temperatures cool with increased elevation during daylight hours, but a strong inversion layer is often the cause of much warmer temperatures (+10 to 15 degrees) at the 1,300 foot level.
During nighttime hours, especially when conditions are dry, the lower elevation temperature is much cooler (-10 to 15 degrees) due to cold air from the Ortega Mountains and Saddleback sinking to the valley floor.
Visit Weather Currents for all your climate information on the "other" side of the Ortega Mountains.
San Juan Capistrano, CA:
Calendar year 2008: With the exception of November and December the year was very dry, unusually so. Rainfall for the calendar year came to about 13 inches, which is five inches less than historical average. November and December accounted for nearly half of the annual rainfall total in a rush to catch-up before the year ended. December's nearly three and one-half inch total rainfall was the most monthly precipitation in several years. Some additional notes for 2008 included two nights below freezing (32 degrees) and three days above 100 degrees. There were 25 days above 90 degrees, seven of which were in October and that was unusual. Both July and August recorded no high temperatures at 90 degrees or above and were considered cooler than normal. The highest temperature was 102 degrees on June 21, and the lowest was 30 degrees six months later on December 27.
The average daytime high temperature was 74 degrees, which is the historical average. The overnight low temperature average was 50 degrees, or 1 degree less than the historical norm.
79 - 33
81 - 32
86 - 36
100 - 39
96 - 45
102 - 49
86 - 53
88 - 59
100 - 54
95 - 37
93 - 37
76 - 30
The average daytime high temperature was 74 degrees, which is the historical average. The overnight low temperature average was 50 degrees, or 1 degree less than the historical norm.
(You may also find the long-range weather prediction article for California of interest.)
In San Juan Capistrano the average annual rainfall total is 18 inches.
Heaviest amounts of rain usually occur between late November and early April. As is usually the case, the winter rain intensity is stronger in the Los Angeles area before December, and then more substantial weather besets San Juan Capistrano area from December through April.
This is evident by monthly average rainfall totals in October and November in the Capistrano Valley, which are less than that of the Los Angeles region, but from December through April the opposite occurs and Los Angeles monthly rainfall totals are less than that of the Capistrano Valley. This is also the case in some valley regions of central California.
San Juan Capistrano sits 137 feet above sea level on the floor of the Capistrano Valley three miles inland from the Pacific Ocean to its South. Unlike many areas in the greater Los Angeles basin fed predominately by SW-W onshore flow; the Capistrano Valley acts as a funnel between the Ortega Mountain foothills (East), and the San Joaquin Hills (West).
Weather in this valley is unique to the coastal climate of southern California. Weather data recorded in one part of the city will differ 1/2 mile away in another location. This explains why observers report varying degrees of temperatures in San Juan Capistrano -- none of which are consistent. For this study, the central business district was used.
Irony best describes the climate in San Juan Capistrano. While much of the year is relatively moderate, extremes can make living conditions uncomfortable to downright hazardous.
Topography plays an important role in San Juan Capistrano's weather patterns. Temperatures and rainfall three miles inland from Santa Monica, or Huntington Beach show statistical data more consistent with coastal weather patterns in California. Landmass in Los Angeles is relatively flat facing the Pacific, allowing constant and predictable coastal influences throughout the year.
The city limits of San Juan Capistrano stretch North of the Pacific five miles, winding around foothills and through canyons. The temperatures can vary from one part of the city to another by as much as 15 degrees at a given time. The indoor comfort difference may require the use of air cooling systems for neighborhoods like the Casitas Capistrano, or Village San Juan, or not, as the case would be in neighborhoods of Stonehill Drive.
The two most notable climate influences are canyon winds, (Santa Ana winds) and the coastal influence from the Pacific. Prevailing winds along southern California's coastline are ocean surface westerlies, which enter exposed coastal plains. However, due to the foothills, and topography of Dana Point, southerly winds prevail much of the year in San Juan Capistrano. It would be considered unusual for summertime afternoons in San Juan Capistrano to be wind-free. If wind dies-off in July-September, the temperature often soars after 3 p.m. Southerly wind speeds average between 10-15 mph in summer months, less in winter months, drawn from the cooler Pacific Ocean air from inland heat.
Man Made Changes?
During the past 30 years, San Juan Capistrano itself has grown in population; however, surrounding areas (Laguna Niguel, Dana Point, and Aliso Viejo) have only just come into existence. Construction of residential areas in Laguna Niguel and Dana Point have altered the landscape of what was once open grassland, deep canyons, and rolling foothills nearly 2,000 feet high. To accommodate more dwellings, engineers devised ways to top-off hills, dropping some elevations by 500 feet, and using the soil to fill-in canyons, thus creating more flat area to construct homes.
The once jagged topography of hills and canyons inland from Dana Point acted to buffer daily westerlies from entering the lower Capistrano Valley. Now with smooth, terraced neighborhoods populating the region, ocean airmasses enter unabated. It is hypothesized that such widespread topography alterations have indeed contributed or caused local climate change, but there is no scientific proof to date to support the claim.
Prior to the massive build-up of Dana Point and Laguna Niguel (pre-1985) summertime westerlies were confined to (almost to the exact cross streets of Del Obisbo and Camino Del Avion) Marco Forster Jr High school and points South. During the 1980s and 1990s as topography changes increased and completed, daily westerlies advanced North.
The southern section of San Juan Capistrano, predominately South of where San Juan Creed Road meets I-5, now experiences the daytime westerly winds. This 2 mile inland migration of cooler westerly winds would eliminate the need for air conditioning in areas where it was once was used. For this region once known for temperature microclimates, it is remarkable that man did alter climate, although unintentionally.
While man-made climate change is one small aspect of larger, natural climate influences; San Juan Capistrano climate remains in the eye of nature. Beginning in late September, high pressure replaces thermal low pressure in the desert regions and inner-mountain West. While summertime heat well inland causes airmasses to rush in from the Pacific Ocean, the opposite effect takes place in Fall. Pressure increases over land, developing airflow towards the Pacific, forcing air through canyons of California.
Santa Ana Winds, Pacific Storms
Santa Ana winds push out to sea, ushering-in dry often hot weather to the region, but this same condition also produces the coldest weather of the year when overnight temperatures can plunge into the 20s even though the daytime high may reach 70.
Lack of moisture from Santa Ana windstorms, allow air to warm and cool rapidly. It is not unusual for daytime temperatures to warm 50 degrees from early morning hours in San Juan Capistrano.
Native Americans who settled in the Capistrano Valley, before Spaniards claimed this area, labeled Santa Ana winds, "Devil Winds." Spaniard diaries and Indian tales of these winds describe gales of which lasted many days, and tell of dust storms that blacked-out the sunshine.
TRULY WACKY WEATHER!The only prominent tornado outbreak occurred during one of the area's wettest Aprils. On 8 April 1965, two (twin as they are called) tornadoes spawned in Capistrano Beach and headed inland, causing property damage and downing of power lines. From eyewitness reports, the tornadoes traveled 1 mile along Del Obispo, and dissipated at Via Belardes.
The period February 1972 to February 1973 brought some of the most spectacular weather to San Juan Capistrano, beginning with a surprise storm on the afternoon of 6 February 1972. Despite that the area was suffering from an unusually dry winter, all the elements fell into place for moist, unstable air to pile against the Santa Ana mountains and produce a powerful thunderstorm over southern Orange County (even to this day I've not witnessed a storm like it anywhere else, including my chases in Kansas and Texas.) By 1 p.m. the area known today as Mission Viejo was experiencing torrential rain and hail, and a real tornado touched down west of El Toro in what today is the Irvine auto park. (At the time the area was grass land.) Highway Patrol officers on the scene were stunned to say the least and halted traffic on Interstate 5.
At 2:30 p.m. the storm had gained in intensity and turned the sky over San Juan Capistrano dark and orange from blowing dust. Westerly winds gusted above 60 mph for ten minutes and then stopped completely. Within a half hour's time, the storm moved over the Capistrano Valley. Thunder boomed, but we did not see lightening. The sky had turned so dark it was not possible to see out from indoors. Winds picked up from the North bringing a deluge of nearly 1 inch of rain, and several rounds of hail. By 4:00 p.m. the storm washed itself out and the sky cleared for sunset. Meanwhile, in Los Angeles, the skies remained fair and sunny all day.
A second surprise in 1972 came with early winter storms across all of California. On the night of 15 November, the San Bernardino and Riverside areas were hard hit with powerful thunderstorms, hail and high winds. The coastal areas experienced the outflow rain and wind from these storms, but daybreak brought fair weather. However, on the night of 17 November, one of the most powerful thunderstorms to hit the Capistrano Valley set-in for three hours. Rainfall of almost 4 inches (3.73 inches) fell on San Juan Capistrano, and Orange County police reported 12 funnel clouds overnight. What was most unusual about this storm was that during the storm's peak, lightening struck in 10 to 15 second intervals. This type of storm is rare for the region, and more like those found in the Midwest.
On 11 February 1973, an early morning squall line developed between Catalina Island and Newport Beach. As it rode southeast and picked up speed, the squall slammed into San Juan Capistrano with 90 mph hour winds -- this storm broke the wind gauge and also pulled a mobile home from its foundation on Alipaz Street -- sheets of hail also accompanied the storm carried by straightline winds. As this thunderstorm developed behind a frontal system, the entire storm total for that weekend approached 2 inches and it brought several inches of snow to San Juan Hot Springs.
The first two weeks of February 1978 was cloudy and warm -- the weather resembled May temperatures which helped to spawn an unusual storm off the Pacific Ocean. On the 9th, a warm-front stalled over Orange County with sustained SE winds of 35-45 mph through the region for 12 hours under cloudy skies. By midnight of the 10th, sustained winds of 65-75 mph were confined to the South Coast (WNW winds blew across Los Angeles county) along with heavy showers. By 2 a.m. on the 10th, peak gusts of 104 mph brought down powerlines, sunk boats in Dana Point Harbor, uprooted trees and caused structural damage across the Capistrano Valley. Rainfall totals for this storm were "estimated" at 2 inches (based upon other totals in the area) because the rain gauge was destroyed from flying debris.
Casitas Capistrano saw a brief tornado touchdown on 6 March 1980, again a Pacific post-frontal squall was to blame for producing the twister. Damage was confined to broken windows and downed trees. Hail and heavy rain accompanied the storm, bringing .62 inches in 20 minutes.
Unusual wet weather has not always been reserved for winter months. In fact, a series of summer-time rains forever altered the area's floral, and is responsible for the boom in wild artichokes.
In August 1977 nearly 3 inches of rain fell, causing native grasses to sprout four months early; and although the grasses dried up before winter rains set-in, a second round of grasses recovered the crop by mid-winter 1978. However, in August 1983, a prolonged spell of hot, humid weather settled into San Juan Capistrano. With high temperatures in the upper 80s and low 90s, and low temperatures in the 70s -- the area experienced three consecutive nights of thunderstorm activity offering more than 2 inches of rain, and highly uncomfortable humidity. The early season rainfall again caused local barley to sprout, but without sustained rainfall the wild grass, once native to the region's foothills, dried up and never recovered. To this day the only remaining annual grass is wild oat, and in the wake of absent barely (which usually grew waist-high,) dandelions, artichoke, and other weeds have take its place.
As the area kept more accurate records by the National Weather Service and farmers; Santa Ana winds were verified to play havoc with plants, animals, and structures. Santa Ana wind top-speeds consistently record below 70 mph, unlike Pacific Ocean storm systems.
It is not unusual in for Santa Ana winds to top 50 mph as early as September and as late as April. These winds will down trees, powerlines, and damage roof shingles. Traditionally, these winds would begin during the early morning hours, and cycle throughout the event, lasting only 8-10 hours, or as much as three days. Winds can gust to 45 mph for five minutes, and drop off to less than 5 mph, before increasing again 30 minutes later. During a cold-snap, and when winds cease, it is not uncommon for a winter nighttime low temperature to plunge into the 20s, damaging tender plants.
People often ask why +70 mph winds from Santa Anas don't do as much damage as a hurricane with the same wind speed. The simple reason for that is the amount of moisture associated with the wind storm itself. While a strong Santa Ana wind can be damaging itself, these winds blow without billions of raindrops propelled at 70 or 100 mph, thus trees and powerlines can better withstand the strong winds without the associated rain. Furthermore due to the nature of soil and rainfall conditions in the tropics, tree roots don't need to reach deep into ground to find a water source as they do in southern California -- deeper roots help to better establish trees against strong wind. Residents of southern California only need to compare the damage between a winter rainstorm with 45 mph winds versus a Santa Ana wind with 70 mph gusts to note this difference.
Pacific storms are the second greatest influence in San Juan Capistrano, with some events bringing heavy rain, and southeasterly gales of 30-50 mph. Pacific storm winds have reached 100 mph more than once in 30 years. One such storm occurred in early February 1978, when winds topped 100 mph and caused extensive damage in San Juan Capistrano, as well as Dana Point. This event was caused by a warm front that stalled over Orange County for several hours.
As with much of southern California, summer months are basically rain-free; however humidity levels remain high and combined with an occasional subtropical influence from Arizona or old Mexico, air temperatures can grow uncomfortable. During the past 30 years weather records indicate that some coastal locations have actually cooled 1-2 degrees from June through August compared with 60 years ago. This information is worthy of a wider study. Overall however, no location below 4,300 feet in elevation across California is reporting annual average temperatures less than they were 60 years ago, with most reporting an increase of 1 degree in the past 30 year cycle.
Hurricanes, Snow, Historical Events
The summer of 1983 was perhaps the most noticeable tropical summer with frequent thunderstorms, sometimes producing an inch of rain overnight in the Capistrano Valley; and persistent hot and humid weather lasted from the middle of July into the middle of September.
For much of the coastal plain of southern California, heat-spells are short-lived. Temperatures in San Juan Capistrano exceed 100 degrees on the average of 1-6 times each year.
In September of 1979, San Juan Capistrano topped 100 degrees 10 consecutive days during a mild Santa Ana wind event. Humidity was low, and overnight temperatures fell into the 60s, helping to make the event bearable for residents.
In mid-September 1972 a major Pacific hurricane headed towards southern California; however only hours before it was expected to strike, it abruptly turned East striking counties South of Tijuana, Mexico, killing thousands, and altering dry canyon landscapes forever.
Southern California has experienced hurricanes in the past. In August 1977, a weakened hurricane struck San Diego and Orange counties with winds of 50 mph and between 2-5 inches of rainfall. San Juan Capistrano received nearly 3 inches of rain with southerly winds of 34 mph.
In September 1939 a full-fledged hurricane struck southern California following two weeks of temperatures in the mid 100-teens. Winds from this hurricane topped 70 mph, and widespread rainfall of 7-15 inches caused extensive damage, and killed hundreds. The Capistrano Valley floor became one massive river. To the North, in Los Angeles, suburbs and the valleys came under water resulting in a massive effort to build flood control channels.
However, this storm failed to match the hurricane of 1861, which is said to have caused massive destruction and many deaths due to flooding. It is not known how much rain fell in the region during this hurricane, although rough estimates show as much as 20 inches of rainfall would have been possible in a 48-hour period.
San Juan Capistrano at the historic Mission has recorded snowfall throughout record keeping. The surrounding foothills are more prone to snow events during the coldest winters. The Winter of 1948-1949 recorded three days of snow, ice, and sleet in San Juan Capistrano, as well as most of southern California. But surrounding foothills above the valley floor were capped in several inches of snow for a week that season, and have since experienced snowflakes periodically.
While Winter 1948-1949 was one of the coldest on record, 1912-1913 experienced even colder temperatures (low teens) with snowfall. Periodic cold snaps throughout the 1900s meant sure devastation to the region's citrus crops. In the height of San Juan Capistrano's farming history, UC Riverside alerted local farmers each Winter to possible frost or freezing temperatures. San Juan Capistrano is one of the coldest valley locations between Ventura County and the Mexican border.
Today, home owners and businesses replace farming, and therefore any extreme weather conditions would only effect garden plants.
Rainfall amounts along the coastal plain from Brentwood South to the Mexican border are relatively low, average about 9 inches, with the exceptions of foothill-enhanced rainfall at some locations (Beverly Hills, Hollywood, Pacific Palisades.) Topography enhances rainfall on the Palos Verdes peninsula, and from Corona del Mar South to Monarch Bay, and again in the area North of Oceanside, primarily Camp Pendleton. Rainfall totals may average between 5-10 inches more only 1 mile away from the Pacific Ocean due to the foothill influence. San Juan Capistrano's seasonal average rainfall is 18 inches, which is more than many inland cities like Los Angeles (16 inches), Santa Ana (14 inches), and Riverside (12 inches), cities of which experience little topographical lift. Additional cities with topographical lift include Beverly Hills (18 inches), Pasadena (22 inches), Trabuco Oaks (25 inches.)
The topography also prevents thick fog events. It is rare for San Juan Capistrano to experience dense valley fog. Unlike other coastal plain locations like Long Beach, or Fallbrook (San Diego County,) if fog descends upon this valley floor it will usually lift or dissipate all together within a couple of hours. But in Dana Point, San Clemente, or Laguna Beach, dense fog may hang overnight causing difficult driving conditions for motorists, and has been blamed for causing massive pile-ups on the Interstates. Tugging wind currents, and the topography help to keep ground fog at a minimum in San Juan Capistrano, whilst high fog is more common and is experienced here at any time of year, especially during springtime, notably called "night and morning low clouds."
As southern California grew, much about historical climate was not known, other than stories passed down through farmers. The big drought of the mid-1860s is said to have been rain-free for nearly 3 years. The series of summertime rainstorms during the late 1890s caused a massive mudslide to the northwest of the city, a hillside scar of which is clearly visible today.
Since the 1960s however, meteorologists have gathered data throughout the region. One surprise notation has been renaming the Los Angeles basin as the Pacific coasts' "Tornado Alley." While it is true that tornadoes in southern California are not like those in Kansas or Texas, some have caused extensive damage and loss of life in Los Angeles and Orange counties.
Tornadoes and Waterspouts
Tornadoes have touched down in San Juan Capistrano. Funnel clouds, and wall clouds have been spotted, sometimes multiple events in one season. However, while tornado events are rare, another event can provide fun for the weather watcher. Waterspouts are common on the Pacific Ocean during winter squalls, and because southern Orange County sticks out into the ocean, squalls will hit the region on their tour southeast. The usual pattern; squalls develop on open water between Catalina Island and Newport Beach and head southeast, building in strength as they approach and make landfall in Laguna Beach.
The faster these storms move across the water on northwesterly gales, land causes them to lift as they bump against the foothills. When waterspouts are present in a storm, they will wrap-around the coastal bend at Dana Point. The Capistrano Valley acts as a vacuum into San Juan Capistrano and for a brief time, air currents feed into the squall from the South giving it more strength as it ploughs over the foothills into the valley. The result is a brief but strong gust front, small hail, and heavy rain (between one-half and three-quarters of an inch in 15-30 minutes.) Wind gusts of 50-60 mph out of the southwest are indicative of the event, and may last up to 10 minutes.
The squall quickly heads east and breaks apart as showers over higher terrain before entering San Diego county.
The extreme weather should not dampen a day in San Juan Capistrano, as most of the year is relatively predictable. It is the two dozen (or so) days when nature does what she wishes that keep local weather watchers remembering that anything is possible.