The Climate of El Cajon, California

Introduction

El Cajon is a city in San Diego County, California located about 15 miles northeast of downtown San Diego. With a population of over 100,000, it is one of the larger cities in the San Diego metropolitan area.

El Cajon has a Mediterranean climate, characterized by warm, dry summers and mild, wet winters. Its proximity to the Pacific Ocean and its location within the rain shadow of coastal mountains strongly influence the city’s climate.

Climate Classification

El Cajon has a hot-summer Mediterranean climate (Köppen climate classification Csa). The Mediterranean climate zone is characterized by hot, dry summers and mild, wet winters. El Cajon experiences warm to hot temperatures and very little rainfall from May to October. The winter months from November to April bring cooler weather, more clouds, and the bulk of annual precipitation.

Key Characteristics

• Hot, dry summers from May to October
• Mild, wet winters from November to April
• Little rainfall in summer
• Moderate rainfall in winter
• Comfortable warm temperatures year-round
• Low humidity most of the year
• Over 300 sunny days per year on average

Weather Averages and Records

Temperatures

El Cajon has warm, pleasant weather year-round owing to its proximity to the Pacific Ocean. Daily average highs range from around 65°F in December and January to over 90°F in August. Daily lows range from 43°F in winter to 62°F in summer. The record high temperature is 118°F, set in July 2018. The record low is 17°F, set in January 1913.

El Cajon Average Temperatures and Extremes:

Month	Average High	Average Low	Record High	Record Low
January	65°F	43°F	88°F (1975)	17°F (1913)
February	66°F	45°F	95°F (1977)	20°F (1913)
March	68°F	48°F	100°F (1983)	28°F (1949)
April	71°F	52°F	104°F (1984)	34°F (1913)
May	74°F	57°F	107°F (1958)	41°F (1909)
June	78°F	61°F	114°F (1960)	48°F (1909)
July	84°F	65°F	118°F (2018)	52°F (1909)
August	87°F	67°F	111°F (1984)	54°F (1891)
September	84°F	64°F	116°F (1963)	48°F (1891)
October	78°F	58°F	113°F (1987)	38°F (1909)
November	71°F	51°F	101°F (1985)	27°F (1913)
December	65°F	43°F	88°F (1975)	17°F (1913)

Precipitation

El Cajon has a winter wet season and a summer dry season typical of Mediterranean climates. Over 80% of annual rainfall occurs from November to March, with very little precipitation falling from May to September. Average annual rainfall is around 11 inches.

The wettest month is February, averaging over 2 inches. The driest month is June, averaging just 0.05 inches. Rainfall can vary dramatically year to year because El Cajon is on the fringe of the region affected by winter storms coming off the Pacific.

Average Monthly Rainfall in El Cajon (inches):

Month	Average Rainfall	Record Rainfall
January	1.98	6.62 (1993)
February	2.35	7.18 (1998)
March	1.30	4.68 (1991)
April	0.75	5.36 (2005)
May	0.24	1.81 (2005)
June	0.05	0.68 (1921)
July	0.04	1.15 (1925)
August	0.05	1.26 (1909)
September	0.24	2.64 (1939)
October	0.35	3.21 (1966)
November	0.98	5.17 (1965)
December	1.50	7.18 (2010)

Sunshine and Cloud Cover

El Cajon enjoys plenty of sunshine all year long. The sunniest months are May through September when clear or mostly clear skies prevail over 75% of the time. The cloudiest months are December through March when increased Pacific storm activity leads to more cloud cover. The city still averages over 60% sunshine even in its cloudiest months. Dense morning fog coming inland from the Pacific is common in May and June.

Average Monthly Sunshine and Cloud Cover in El Cajon:

Month	% Sunshine	% Cloud Cover
January	69%	31%
February	72%	28%
March	75%	25%
April	79%	21%
May	83%	17%
June	88%	12%
July	93%	7%
August	93%	7%
September	89%	11%
October	81%	19%
November	74%	26%
December	64%	36%

Humidity

El Cajon experiences comfortable, dry conditions for most of the year. Average relative humidity ranges from 50% in winter to around 75% in early morning hours during the summer marine layer season. The highest risk of humid, muggy conditions occurs in late summer when the marine layer clashes with seasonal heat. Episodes of Santa Ana winds can also boost temperatures while lowering humidity to dangerously dry levels.

Seasonal Weather

El Cajon’s Mediterranean climate leads to four distinct seasons.

Winter (December – February)

Winters are mild and wet in El Cajon. Average highs are in the mid 60s F and average lows in the low to mid 40s F. Rainfall averages 4-5 inches over the three-month period, coming from Pacific storms and occasional tropical weather systems. Heavy rain leading to flooding is possible during major storm events like atmospheric rivers.

The winter storm track also brings more cloud cover, with sunshine 60-75% of days. Winter mornings often start out foggy. Frost is rare in town but can occur in nearby valleys and foothills. Snowfall is extremely rare, occurring perhaps once per decade. Overall, winters offer comfortable daytime conditions for outdoor recreation with cool nights requiring light jackets.

Spring (March – May)

Spring brings warmer and drier conditions to El Cajon. Average high temperatures climb into the low 70s F by April and mid 70s F by May. Overnight lows range from the upper 40s to mid 50s F. Rainfall decreases markedly but spring still sees occasional Pacific storms and showers. May gray can bring dense coastal morning fog.

Humidity remains relatively low and sunny skies prevail most days. By late spring, warm and dry offshore Santa Ana winds increase in frequency. Spring offers ideal weather for outdoor activities with plenty of sunshine and comfortably warm afternoons.

Summer (June – August)

Summers in El Cajon are hot, dry, and sunny. Average high temperatures reach the upper 80s F in June and exceed 90 F in July and August. Low temperatures only drop into the 60s F, offering little nighttime relief from the heat. Rainfall is scant, averaging less than 0.5 inches over three months.

Dry vegetation and low humidity increase wildfire risk. June often sees coastal morning fog and clouds that retreat inland during the afternoon. By mid summer this marine layer dissipates and sunny skies prevail. Monsoonal moisture can spark thunderstorms at times. Hot weather is punctuated by occasional heat waves and Santa Ana wind events that send temperatures soaring over 100F.

Fall (September – November)

Fall brings a transition back toward cooler, wetter weather. September maintains hot summer conditions, though thermal extremes decrease from August peaks. October daytime temperatures drop into the upper 70s F while overnight lows return to the 50s F. The first Pacific storms typically arrive in November, with rainfall averaging 1-2 inches monthly.

However, warm and dry weather can persist deep into fall during late onset winters. Santa Ana winds pick up in October and November, raising wildfire risk. Outside of windy periods, fall offers ideal weather for outdoor recreation with comfortably warm afternoons and cool evenings.

Local Climate Influences

El Cajon’s climate is shaped by its geography within the greater San Diego region. Proximity to the Pacific Ocean and location within coastal mountains are the main drivers.

Pacific Ocean Influence

The Pacific Ocean has a moderating effect on El Cajon’s climate year-round. Water temperatures offshore of San Diego average in the low 60s F in winter and low 70s F in summer. This enormous heat sink keeps coastal land areas cooler in summer and warmer in winter compared to inland desert regions. The ocean influence tempers extremes in El Cajon’s weather. Cities farther inland experience greater seasonal swings in temperature.

During spring and early summer, the warm offshore California Current pushes cool surface water toward shore. This creates the marine layer of low clouds, fog, and humidity affecting the coast. By late summer the ocean warms, dissipating the marine layer. But the ocean remains cooler than land, causing sea breezes that moderate afternoon heat.

Rain Shadow Effect

El Cajon lies within a rain shadow east of coastal mountains. Wet winter storms coming off the Pacific Ocean rise up coastal topography, causing heavy rainfall on west-facing slopes. As clouds crest the mountains they descend, warm, and dissipate – casting minimal precipitation over inland valleys and foothills in the rain shadow. Just 15 miles inland, El Cajon averages 50-75% less rainfall than coastal San Diego. The rain shadow effect contributes to El Cajon’s hot, dry summers.

Santa Ana Winds

El Cajon periodically experiences hot, dry Santa Ana winds, especially in fall and winter. These offshore flows originate from high pressure over the Great Basin. Air is funneled through mountain passes and canyon gaps, warming and compressing adiabatically as it descends toward sea level. The arid winds boost temperatures and lower humidity, worsening wildfire conditions. Wind gusts commonly exceed 50 mph, causing dust storms and toppling trees and power lines.

Microclimates

Within El Cajon there are noticeable local microclimates. Lower elevation valley areas tend to be warmer than surrounding foothills and mountains. But at night this pattern reverses as cold air drains from higher terrain into low-lying zones prone to frost. North-facing slopes receive less sunshine so exhibit cooler conditions. Urban centers like downtown absorb more solar radiation during the day. The urban heat island effect can make city centers several degrees warmer than rural outskirts overnight.

Climate Change Projections

Climate change will alter El Cajon’s weather and environment in the coming decades. Based on current emissions trajectories and climate modeling, scientists project the region will experience:

• 2°F to 5°F increase in average temperatures
• More frequent extreme heat days and heat waves
• 5% to 15% decline in total annual rainfall
• Dramatic decrease in spring snowpack in nearby mountains
• Up to 100 additional wildfire risk days per year
• Expansion of vector habitats increasing disease risk
• Continued drought stress on water supply reservoirs

These changes will compound existing hazards like heat waves, wildfires, and droughts. Adaptation strategies will be required to increase El Cajon’s resilience and reduce risks to residents.

Impact on Lifestyle

El Cajon’s mild Mediterranean climate makes for a comfortable lifestyle year-round. Abundant sunshine and warm weather provide ample opportunity to enjoy outdoor recreation in parks, canyons, and nearby mountains and deserts. But some extreme weather events pose hazards.

Outdoor Activities

Pleasant weather prevails in El Cajon most of the year. Parks and trails are popular outlets to enjoy sunshine and nature. Summers offer ideal weather for swimming, boating and water sports at area lakes, as well as camping and hiking in the Laguna Mountains. Golf is popular year-round. Winter rains support colorful displays of spring wildflowers. Offshore Santa Ana winds attract windsurfers and kiteboarders. Overall the climate enables an active outdoor lifestyle nearly any time.

Gardening

The long growing season and minimal winter frost make gardening feasible year-round. Citrus trees, bougainvillea, succulents, palm trees, and other heat and drought tolerant plants thrive. Vegetable gardens require irrigation in summer. Some warmer microclimates support tropical species like bananas and avocados. Flower gardening is especially popular. But periodic droughts and water restrictions can limit landscapes.

Hazards

El Cajon’s climate poses some hazards to consider:

• Santa Ana wildfire risk is high from September to November with extreme winds and dry vegetation. Over a dozen major wildfires have impacted the area since the 1970s.
• Droughts are a regular occurrence, often lasting multiple years. Severe drought stresses water supplies and increases wildfire risk.
• Heat waves bring dangerous temperatures over 100°F, made worse by low humidity and concrete urban heat islands. Vulnerable populations like the elderly face health risks.
• Flash floods and mudslides in nearby canyons and burn areas can occur during heavy winter storms. Damaging winds accompany storms.
• Earthquakes pose a major hazard in seismically active Southern California. Major fault lines traverse the region.

Proper adaptation and emergency preparedness are necessary to mitigate climate hazards. Advanced warning systems for extreme heat and fire weather help reduce risks.

Conclusion

El Cajon enjoys a comfortable Mediterranean climate characterized by sunny, mild weather and minimal extreme weather events. Its proximity to the Pacific Ocean and rain shadow location create pronounced dry summer and wet winter seasons.

Climate change will lead to warming summer temperatures, periods of more intense drought, and other impacts in coming decades. But El Cajon will remain one of the most favorable climates in the country overall. The Mediterranean climate helps support a laid-back outdoor lifestyle that makes the city an appealing place to live and visit year-round.