Climate of San Diego facts for kids

The climate of San Diego, California is often called a hot-summer Mediterranean climate. This means it has hot, sunny, and dry summers. Winters are cooler and wetter. However, San Diego is much drier than most other places with this climate type. Even its winters are quite dry.

San Diego's Temperatures

San Diego's average monthly temperatures change throughout the year. In January, the average is about 57.3 °F (14.1 °C). In August, it rises to about 72 °F (22 °C).

Most days in San Diego are warm. About 344 days a year are warmer than 60 °F (16 °C). But only about 25 days get hotter than 80 °F (27 °C).

The hottest time of year is usually late summer and early autumn. The average high temperature is 78 °F (26 °C) in August and 77 °F (25 °C) in September. Sometimes, temperatures can reach 90 °F (32 °C) or even higher. Snow and ice are very rare, especially near the coast. They usually only happen further inland during winter.

Morning Clouds and Fog

San Diego often has marine layer clouds. These clouds appear most often between May and August. They make mornings cool, cloudy, and sometimes foggy. The clouds usually disappear as the sun gets stronger. People in San Diego have sayings like "May gray" and "June gloom." These refer to how the morning fog often lasts longer in May and June. Sometimes, the cool, cloudy weather can even stay all day.

Hot Winds: Santa Anas

Very high temperatures are rare in San Diego. They usually happen when "Santa Ana winds" blow. These are hot, dry winds that come from the deserts inland. These winds make October a "fire season" for San Diego and Southern California. This is because there's little rain and sudden heat waves. For example, the highest temperatures ever recorded were 111 °F (44 °C) in September and 107 °F (42 °C) in October.

The hottest temperature ever recorded in San Diego was 111 °F (44 °C). This happened on September 26, 1963. It was tied on September 27, 2010. The coldest temperature ever recorded was 25 °F (−4 °C) on January 7, 1913.

Rainfall in San Diego

San Diego gets about 146 sunny days and 117 partly cloudy days each year. The average yearly rainfall is less than 12 inches (30 cm). This makes the climate almost arid (very dry). Most of the rain falls in the cooler months, from December to March. Even then, San Diego gets less rain than other parts of the U.S. west coast.

Summers are usually very dry with almost no rain. However, sometimes humid air from the North American Monsoon brings thunderstorms for a few days in summer. The amount of rain can change a lot from year to year and month to month. San Diego can have both droughts (very dry periods) and floods (heavy rain).

Tropical Storms and Hurricanes

While full hurricanes are very rare, San Diego gets more tropical storms than any other place in California. These storms can bring several inches of rain and strong winds. Famous examples include the 1858 San Diego Hurricane and the 1939 California tropical storm. The remains of Hurricane Kathleen in 1976 also brought heavy rain.

Inland areas like El Cajon can get over 20 inches (51 cm) of rain each year. Higher up in the Cleveland National Forest, some areas like Palomar Mountain average more than 40 inches (100 cm) of rain per year.

On average, San Diego has about 41 days with measurable rain. The wettest year was 1941, with 24.93 inches (63.3 cm) of rain. The driest year was 1953, with only 3.23 inches (8.2 cm). The most rain in one month was 9.09 inches (23.1 cm) in January 1993. The most rain in 24 hours was 3.23 inches (8.2 cm) on April 5, 1926.

Snow in San Diego

Snow rarely falls in San Diego's low-lying areas. It has only been recorded five times in over 125 years. The last time snow flurries were seen was on February 14, 2008, at higher elevations (around 1,700 to 1,800 feet (520 to 550 m)). The last time measurable snow fell in some neighborhoods was on December 13, 1967. In winter, light snow is common in the mountains of east and north San Diego County, above 3,000–4,000 feet (910–1,220 m).

Local Climate Differences

The climate in San Diego can change a lot over short distances. This is because of the city's hills, mountains, and canyons. This creates "microclimates." For example, during "May gray / June gloom," the thick "marine layer" clouds keep the coast cool and damp. But just a few miles inland (about 5 and 15 miles (8 and 24 km)), the sun will be shining brightly. Cities like El Cajon and Santee rarely have the same cloud cover as the coast.

San Diego vs. National Averages

San Diego's weather is quite different from the rest of the United States.

• San Diego sees about 21 days with rain each year. The national average is about 110 days.
• San Diego has about 267 mostly sunny days. The national average is 213.
• San Diego gets 0 inches of snow per year. The national average is about 24.2 inches (610 mm).
• San Diego has only about 2.5 days above 90 °F (32 °C). The national average is 37.9 days.
• San Diego has 0 days below 32 °F (0 °C). The national average is 88 days.
• The average low temperature in January for San Diego is 50 °F (10 °C). The national average is 26.5 °F (−3.1 °C).
• The average high temperature in July for San Diego is 76 °F (24 °C). The national average is 86.8 °F (30.4 °C).

Climate Data

Ocean Temperatures

The average yearly ocean temperature off San Diego is 65 °F (18 °C). It ranges from 59 °F (15 °C) in January to 72 °F (22 °C) in August. Scientists have noticed that water temperatures at Scripps Pier have gone up since 1950.

More About Santa Ana Winds

The months from September to April can bring warm, dry winds called "Santa Anas" from the desert. These winds happen about 10 days a year. They bring hot, very dry conditions. Inland, and in mountain passes, these winds can blow in gusts up to 100 miles per hour (160 km/h). They can also make the air very dry. Near the coast, they usually don't gust over 40 miles per hour (64 km/h).

Santa Ana winds can make wildfires spread and get worse. These winds blow from east to west. Many people think they pull hot air from the desert. However, sometimes the coast can be even hotter than the desert during a Santa Ana event. This is because the air gets warmer as it is pushed down from higher altitudes (like the Great Basin and Rocky Mountains) to sea level. This compression makes the air temperature rise.

El Niño and La Niña Effects

San Diego's wet winter season is affected by something called the El Niño Southern Oscillation.

• During the El Niño phase, San Diego gets more winter storms. The weather is also warmer and more humid.
• During the La Niña phase, San Diego becomes drier. The weather is also cooler and less humid.

Ultraviolet Index

The Ultraviolet index measures how strong the sun's UV rays are.