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California has 5 major types of climate based on altitude, latitude, proximity to the coast, and topography. Deserts account for ~39,000 sq miles (101,000 sq km) of California’s total area of ~163,695 sq miles (423,970 sq km), which is nearly 25%. So, when does it rain in California?
Generally, it rains in California during the winter months. However, the annual rainfall and the total number of days of precipitation vary substantially in the state. California is among the few regions in the world with diverse climates across many areas in proximity.
The specific period and quantum of rain in California can vary between regions that are barely a dozen miles apart in distance or a couple in elevation. Also, neither is California a desert nor is it a Mediterranean haven. Read on to know when it rains in California and if it has a rainy season.
Does California Have a Rainy Season?
Most regions of California have a rainy season beginning in October and extending to April that accounts for around 90% of the annual precipitation. However, many parts of the state receive around 50% of the annual precipitation from December to March.
Despite the normal rainfalls recorded over the years, whether it is the annual precipitation level or seasonal pattern, California doesn’t necessarily have a predictable rain calendar, especially in the south. That’s primarily due to the effects of the El Nino and La Nina climate patterns.
- El Nino causes more rainfall in California, particularly in the south, which is otherwise more adversely affected by La Nina.
- La Nina has the opposite effect of El Nino, causing less rainfall in Southern California and, thus, leading to drier winters.
- Although El Nino is a more frequent climate pattern than La Nina off the California coast and over the Pacific Ocean, both phenomena can last up to 12 months and, sometimes, longer.
- La Nina is the most significant climate factor influencing and triggering drought in many parts of California, which can be worsened by depleting groundwater levels, increasing temperatures, and the shrinking of the Colorado River.
Irrespective of the effects of El Nino and La Nina, California doesn’t have a typical rainy season in a few regions. Also, most parts of California don’t receive even remotely as much rain as the Northeastern and Northwestern U.S.
California Doesn’t Have a Statewide Rainy Season
California has 5 distinct types of climate with up to a dozen variations of these major patterns, including the following:
- Alpine: Highland, timberline.
- Continental: Cool, cold, dry, wet.
- Desert: Arid, hot, semi-arid.
- Mediterranean: Variations.
- Steppe: Hot but not dry.
These local climate patterns depend on many factors. Consider coastal proximity, for example.
Coastal proximity is the most important factor for California’s Mediterranean climate, but there is some localized variation, such as the following:
- California’s Mediterranean climate along the Pacific coast and on the western slopes of the Sierra Nevada has cool summers and winters.
- Some coastal areas have frequent fogs in the summer that isn’t the case for the interior valley, which has cooler winters and warmer summers.
- But all these regions in California with a Mediterranean climate have a rainy season in the winter, from October-November to March-April.
- Plus, many of these places in California receive some rain during the summer months as well, albeit that’s not much by any standards.
While coastal proximity is the major factor for the Mediterranean climate variations in California, the continental and highland weather conditions have multiple local influences, such as:
- Altitude or elevation
- Latitude and temperature
- Prevailing winds
- Slope and its aspect
The slope and its aspect for a region have a significant impact on rainfall and the rainy season in some regions of California, such as Modoc and Sierra.
Here’s how slope and its aspect affect the rain:
- Slopes facing north are cooler and wetter.
- Southern slopes are drier and warmer.
- Western slopes receive more rain.
Hence, the cool continental and highland climate patterns have local variations affecting rainfall or annual precipitation and the precise beginning and end of the rainy season.
Likewise, California’s desert climate has variations:
- The mountains or elevated ranges of the arid and semi-arid regions receive more rain than the places at lower elevations, such as valleys.
- Thus, the Mojave Region doesn’t have only arid and dry but also semi-arid and relatively wet places.
- The San Joaquin Valley has hot summers, not very different from Colorado, Great Basin, and Mojave deserts, but the Steppe climate pattern brings in more rain there.
Furthermore, the rain in California depends heavily on storms and macro climate patterns that make the moderate annual precipitation in different regions vulnerable to significant fluctuation and unpredictability.
Southern California Has Unusual Monsoon Showers
Southern California doesn’t have a monsoon season per se. However, the region may have a few unusual monsoon showers from July through September and, sometimes, in October. Such spells of rain and thunderstorms are usually isolated and often don’t cause a lot of precipitation.
How Much Rain Does California Receive?
The annual precipitation in California is disparate for the distinct climates across the regions, so an assessment of total rainfall during the rainy season should be specific to an area or city.
Here are a few cities representing every climate zone of California and their precipitation during the rainy season in inches:
|City | Month||October||November||December||January||February||March||April|
This table doesn’t reflect either extreme of California’s rainy season, so it isn’t highlighting the driest and wettest places in the state.
For instance, Gasquet and Smith River receive much more rain than the likes of Los Angeles or San Francisco, whereas Death Valley and Stovepipe Wells barely have any precipitation. These are the primary factors that make rainfall patterns different from other regions on the Pacific Ocean. For example, Washington is also on the Pacific Ocean but you get heavy rainfalls in some cities like Seattle. [ Why Does It Rain So Much in Seattle / How Much Rain Does Seattle Get]
Here’s a glimpse of the contrasting rainy seasons of these driest and wettest places in California:
|Month | Place||Gasquet||Smith River||Death Valley||Stovepipe Wells|
|October||5.68 inches (144.27 mm)||5.46 inches (138.68 mm)||0.12 inches (3.04 mm)||0.09 inches (2.28 mm)|
|November||11.77 inches (298.95 mm)||10.52 inches (267.20 mm)||0.10 inches (2.54 mm)||0.09 inches (2.28 mm)|
|December||18.18 inches (461.77 mm)||14.80 inches (375.92 mm)||0.26 inches (6.60 mm)||0.14 inches (3.55 mm)|
|January||13.71 inches (334.51 mm)||11.96 inches (303.78 mm)||0.37 inches (9.39 mm)||0.23 inches (5.84 mm)|
|February||12.13 inches (308.10 mm)||9.32 inches (236.72 mm)||0.52 inches (13.20 mm)||0.55 inches (13.97 mm)|
|March||12.67 inches (321.81 mm)||10.09 inches (256.28 mm)||0.25 inches (6.35 mm)||0.21 inches (5.33 mm)|
|April||8.16 inches (207.26 mm)||8.31 inches (211.07 mm)||0.10 inches (2.54 mm)||0.11 inches (2.79 mm)|
While California’s rainy season coincides with winter, the state receives negligible precipitation during the summer, when it is the driest region in the country. Plus, the annual precipitation, or the number of days it rains across most of California, is dismally low compared to most states.