Climate - San Diego (California)

The climate of San Diego is arid sub-tropical, with very mild, relatively rainy winters and warm, sunny summers. The city is located on the coast of California, in the far south-west of the United States, on the border with Mexico. Despite the low latitude (32 degrees north latitude), the climate is so mild, spring-like most of the year, because a cold current flows on the Pacific coast.
However, the temperature can increase a lot when the Santa Ana blows, the wind from the deserts of inland areas.
At the Lindbergh Field International Airport, located on the coast, the cold record from 1981 to 2020 is 0.5 °C (33 °F), set in December 1988, while the heat record is 41.5 °C (107 °F), set in September of the same year.
Here are the average temperatures.

Rainfall in San Diego is scarce, given that it amounts to just 250 millimeters (9.8 inches) per year, so it is at a semi-desert level. However, the rainfall pattern is similar to that of the Mediterranean climate, but with a drier autumn, since most of the rain falls from December to March, while in summer it hardly ever rains. The wettest month is February. Here is the average rainfall.

The amount of sunshine in San Diego is good all year round, but especially in winter, when the sun shines 75% of the time. The least sunny months are May and June, due to the morning fog that forms on the coast and in the neighborhoods up to about 15 km (9 miles) away from the coast (the phenomenon is called June gloom, even though it actually occurs in May and June, and sometimes in July). In total, there are 3,000 hours of sunshine per year. Here are the average sunshine hours per day.



Due to the aforementioned cold current, the sea in San Diego remains a bit cold even in summer: from July to October, the water temperature is of 19.5/20.5 °C (67/69 °F). Here is the average sea temperature.

In the inland areas, in the towns of San Diego county that in fact are part of the conurbation of the same city, the climate becomes more continental: winter nights are colder (sometimes the night minimum drops around freezing or even slightly below), while the days are warmer all year round.
Moreover, very hot days, with highs of 35 °C (95 °F) and more, are decidedly more frequent. In September 2010, 45 °C (113 °F) were reached (while at the international airport, the temperature didn't exceed 35 °C or 95 °F).
Here are the average temperatures at the Gillespie Field airport, near the town of El Cajon, about 28 km (17 mi) from the coast.

Best Time

Having a great climate, San Diego can be visited all year round. However, from December to March, it can rain, and it can get a bit cold at night, especially in inland areas. In May and June, there may be morning mists. In summer, but especially in September and October, there can be very hot days, when the wind blows from the desert.
The best time to go to the beach is from July to October, when the sea is less cold.

Back to California.

San Diego - Weather by month

Based on the period 1991-2020

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In January, the weather in San Diego is usually mild. The average temperature is of 14.5 °C (58 °F), with a minimum of 9.5 °C (49 °F) and a maximum of 19.6 °C (67.3 °F).
On the coldest nights of the month, the temperature usually drops to around 6 °C (42.5 °F). However, it dropped to 1.7 °C (35.1 °F) in January 2007.
On the warmest days of the month, the temperature usually reaches around 26 °C (79 °F). However, it reached 30.6 °C (87.1 °F) in January 2005.
Precipitation amounts to 50 mm (2 in), distributed over 6 days.
The day lasts on average 10 hours and 20 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 75% of the time.
The average humidity is 64%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 15 °C (59.5 °F). Therefore, the sea is cold for swimming.

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In February, the weather in San Diego is usually very mild. The average temperature is of 14.9 °C (59 °F), with a minimum of 10.3 °C (50.6 °F) and a maximum of 19.5 °C (67.1 °F).
On the coldest nights of the month, the temperature usually drops to around 7 °C (45 °F). However, it dropped to 3.3 °C (37.9 °F) in February 2020.
On the warmest days of the month, the temperature usually reaches around 26 °C (79 °F). However, it reached 32.2 °C (90 °F) in February 1995.
Precipitation amounts to 55 mm (2.2 in), distributed over 7 days.
The day lasts on average 11 hours and 5 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 73% of the time.
The average humidity is 66%.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 15 °C (59 °F). Therefore, the sea is cold for swimming.

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In March, the weather in San Diego is usually very mild. The average temperature is of 15.8 °C (61 °F), with a minimum of 11.9 °C (53.4 °F) and a maximum of 19.8 °C (67.6 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 8.5 °C (47 °F). However, it dropped to 5.6 °C (42.1 °F) in March 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 26.5 °C (80 °F). However, it reached 32.8 °C (91 °F) in March 2004.
Precipitation amounts to 35 mm (1.4 in), distributed over 6 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 8.5 hours of sunshine per day. So, the sun shines 70% of the time.
The average humidity is 67%.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 15.5 °C (59.5 °F). Therefore, the sea is cold for swimming.

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In April, the weather in San Diego is usually very mild. The average temperature is of 17.1 °C (63 °F), with a minimum of 13.3 °C (55.9 °F) and a maximum of 20.8 °C (69.5 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 10.5 °C (50.5 °F). However, it dropped to 7 °C (44.6 °F) in April 1999.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 28 °C (82.5 °F). However, it reached 36.7 °C (98.1 °F) in April 2009.
Precipitation amounts to 15 mm (0.6 in), distributed over 4 days.
The day lasts on average 13 hours and 0 minutes.
There are on average 9 hours of sunshine per day. So, the sun shines 71% of the time.
The average humidity is 66%.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 16 °C (60.5 °F). Therefore, the sea is cold for swimming.

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In May, the weather in San Diego is usually warm. The average temperature is of 18.2 °C (65 °F), with a minimum of 15.3 °C (59.5 °F) and a maximum of 21.2 °C (70.1 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 12.5 °C (55 °F). However, it dropped to 8.9 °C (48 °F) in May 1995.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 26.5 °C (79.5 °F). However, it reached 36.1 °C (97 °F) in May 2014.
Precipitation amounts to only 7 mm (0.3 in), distributed over 2 days.
The day lasts on average 13 hours and 55 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 58% of the time.
The average humidity is 70%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 17 °C (62 °F). Therefore, the sea is cold for swimming.

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In June, the weather in San Diego is usually warm. The average temperature is of 19.4 °C (67 °F), with a minimum of 16.6 °C (61.9 °F) and a maximum of 22.2 °C (71.9 °F).
On the coldest nights, the temperature usually drops to around 14.5 °C (58.5 °F). However, it dropped to 10.6 °C (51.1 °F) in June 2013.
On the warmest days, the temperature usually reaches around 27 °C (80.5 °F). However, it reached 35.6 °C (96.1 °F) in June 2006.
Precipitation amounts to only 1 mm (0 in), and all occurs in one day.
The day lasts on average 14 hours and 20 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 8 hours of sunshine per day. So, the sun shines 56% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 18 °C (64.5 °F). Therefore, the sea is cold for swimming.

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In July, the weather in San Diego is usually warm. The average temperature is of 21.3 °C (70 °F), with a minimum of 18.6 °C (65.4 °F) and a maximum of 24.1 °C (75.4 °F).
On the coldest nights of the month, the temperature usually drops to around 17 °C (62 °F). However, it dropped to 15 °C (59 °F) in July 1995.
On the warmest days of the month, the temperature usually reaches around 28.5 °C (83 °F). However, it reached 37.2 °C (99 °F) in July 2006.
Precipitation amounts to only 2 mm (0.1 in), and all occurs in one day.
The day lasts on average 14 hours and 0 minutes.
There are on average 10 hours of sunshine per day. So, the sun shines 70% of the time.
The average humidity is 75%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 19.5 °C (67.5 °F). Therefore, the sea is very cool for swimming.

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In August, the warmest month of the year, the weather in San Diego is usually warm. The average temperature is of 22.3 °C (72 °F), with a minimum of 19.4 °C (66.9 °F) and a maximum of 25.2 °C (77.4 °F).
On the coldest nights of the month, the temperature usually drops to around 17.5 °C (63.5 °F). However, it dropped to 15.6 °C (60.1 °F) in August 1999.
On the warmest days of the month, the temperature usually reaches around 29.5 °C (85 °F). However, it reached 34.4 °C (93.9 °F) in August 1991.
Precipitation amounts to only 0 mm (0 in), so on average it never rains in the whole month.
The day lasts on average 13 hours and 20 minutes.
There are on average 9.5 hours of sunshine per day. So, the sun shines 71% of the time.
The average humidity is 75%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 20.5 °C (69 °F). Therefore, the sea is cool for swimming.

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In September, the weather in San Diego is usually warm. The average temperature is of 22.0 °C (72 °F), with a minimum of 18.6 °C (65.6 °F) and a maximum of 25.3 °C (77.6 °F).
On the coldest nights, the temperature usually drops to around 16 °C (61 °F). However, it dropped to 13.9 °C (57 °F) in September 1993.
On the warmest days, the temperature usually reaches around 32.5 °C (90.5 °F). However, it reached 38.3 °C (100.9 °F) in September 2012.
Precipitation amounts to only 3 mm (0.1 in), and all occurs in one day.
The day lasts on average 12 hours and 20 minutes.
There are on average 8.5 hours of sunshine per day. So, the sun shines 68% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 20.5 °C (69 °F). Therefore, the sea is cool for swimming.

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In October, the weather in San Diego is usually warm. The average temperature is of 20.1 °C (68 °F), with a minimum of 16 °C (60.8 °F) and a maximum of 24.2 °C (75.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 12.5 °C (54.5 °F). However, it dropped to 6.7 °C (44.1 °F) in October 2019.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 31 °C (88 °F). However, it reached 37.2 °C (99 °F) in October 1994.
Precipitation amounts to 13 mm (0.5 in), distributed over 2 days.
The day lasts on average 11 hours and 20 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 69% of the time.
The average humidity is 68%.
The average wind speed is 9 kph (5 mph).
The average sea temperature is of 19.5 °C (67 °F). Therefore, the sea is very cool for swimming.

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In November, the weather in San Diego is usually very mild. The average temperature is of 17.0 °C (63 °F), with a minimum of 12 °C (53.7 °F) and a maximum of 22 °C (71.6 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 8 °C (46.5 °F). However, it dropped to 3.9 °C (39 °F) in November 1994.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 29.5 °C (85 °F). However, it reached 38 °C (100.4 °F) in November 2010.
Precipitation amounts to 20 mm (0.8 in), distributed over 4 days.
The day lasts on average 10 hours and 30 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 73% of the time.
The average humidity is 63%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 17.5 °C (64 °F). Therefore, the sea is cold for swimming.

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In December, the coldest month of the year, the weather in San Diego is usually mild. The average temperature is of 14.3 °C (58 °F), with a minimum of 9.2 °C (48.6 °F) and a maximum of 19.4 °C (66.9 °F).
On the coldest nights of the month, the temperature usually drops to around 5.5 °C (41.5 °F). However, it dropped to 3.3 °C (37.9 °F) in December 1992.
On the warmest days of the month, the temperature usually reaches around 25 °C (77 °F). However, it reached 28.3 °C (82.9 °F) in December 2004.
Precipitation amounts to 40 mm (1.6 in), distributed over 6 days.
The day lasts on average 10 hours and 0 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 7.5 hours of sunshine per day. So, the sun shines 75% of the time.
The average humidity is 63%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 16 °C (60.5 °F). Therefore, the sea is cold for swimming.