Monsoonal Moisture on Southern California

While the North American monsoon season is typically associated with the Desert Southwest, the heavy rain can also impact Southern California at times. Here is a look at how this weather pattern impacts the southern edge of the Golden State.

Typical Summer Weather for Southern California

The summer season is generally tame in Southern California. The region is known for its sunny skies and moderate temperatures near the coast. The bulk of this part of the state enjoys a Mediterranean climate featuring wet winters and dry and warm summers. Unlike many other parts of the U.S. that have to dodge thunderstorms during the afternoon and evening hours, the major cities in Southern California do not face high humidity levels or persistent rain during the summer months. Instead, the coastal areas usually see clouds in the morning that tend to burn off as the temperature rises during the peak afternoon heating hours.

However, the same North American monsoon pattern that impacts the southwestern U.S. can also wreak havoc across Southern California at times. For instance, the National Weather Service (NWS) recorded nearly 9,000 lightning discharges in San Diego County on August 10 and 11. The majority of the strikes were recorded inland as the rain poured down in some of the higher elevations of the county.

Understanding the Monsoon Season

Monsoon storms happen all over the world. The most pronounced of these weather patterns happen across Asia and India, sending immense amounts of rain across this corner of the globe. For example, the state of Goa in India may not pick up any rain between January and March while almost 94 inches of rain falls on average between June and August. This is more than most places in the world record in a year.

Although most people recognize monsoon storms by their rain, the pattern is actually the result of a seasonal change in wind direction. The shift in the winds results in regular bouts of rain or persistently dry weather that lingers for months.

It is important to remember that monsoonal moisture is highly seasonal in nature. The flow of moisture increases when the winds come off the ocean and onto land, bringing a surge of moisture that serves as the fuel for the seasonal rainfall.

The North American monsoon sets up when moist air is ushered to the north from Mexico and the Gulf of California, the Pacific Ocean, and the Gulf of Mexico. This surge of moisture creates heavy rain and storms for a number of major cities in the Southwest, including Las Vegas, Phoenix, and Albuquerque.

This season begins in the northwestern corner of Mexico in June and gradually moves to the north into the Southwest by July. You can expect the North American monsoon season to wrap up in September.