It might seem intuitive that most homes in coastal California are not equipped with air conditioners because temperatures don't get that hot along the coast. Well, sometimes it does get into the 90s or even 100s during heat waves.

What You Need To Know

  • Daily maximum temperatures usually last less than an hour

  • The sea breeze transports cool ocean air to coastal cities

  • Coastal cities reach temperatures in the 90s only on big heat waves

  • Marine layer clouds help cool temperatures by blocking the sun

During last week's heat wave many coastal cities reached temperatures in the 90s. Even though temperatures seem hot at first glance, these temperatures don't tell the whole story by themselves.

Yes, 90 degrees is hot, but along the coast in California, the daily maximum temperature peaks and then quickly drops off because of the sea breeze. 

Let's look at the temperature for LAX, which is right on the coast. Last Friday, for example, the temperature peaked at 92 degrees at noon. An hour later, the temperature dropped down to 86 degrees. By 7:00 p.m., temperatures were in the 70s.

Maximum temperatures usually last less than an hour before the sea breeze kicks in and cools things down by several degrees.

Coastal Temperatures

Now compare that to the the same 12-hour period for Riverside in the Inland Empire of Southern California. Riverside is just under 60 miles from the coast.

Riverside was in the 90s from noon until 6:00 p.m. That's several hours of hot temperatures. You definitely need an air conditioner to cool you off. 

Inland Temperatures

The farther you are inland, the longer it takes for the sea breeze to reach you, and in turn, cool you off. This also gives the sun more time to heat the land, which heats the air. This is one more reason inland temperatures are warmer than coastal temperatures.

The cooldown is courtesy of Mother Nature's air conditioner: The sea breeze. The sea breeze transports cool ocean air into coastal cities. The air over the ocean is cool because ocean surface temperatures are cool.

Keep in mind that the air above a surface takes on the characteristics of the surface below. 

It is the ocean that cools the air along the coast in California. Ocean temperatures in Southern California usually peak in the low 70s. For most of the year, ocean temperatures are in the 50s and 60s. The all-time highest recorded temperature off the San Diego coast is 79.5 degrees.

This translates into a constant supply of cool air flowing from the ocean to cities near the coast. That's why the cool breeze has been nicknamed "Mother Nature's AC".

Cool Ocean Equals Cool Air

The best advice for those heading to the beach when it is hot and sunny inland is to bring a jacket or sweatshirt. You will need it. Interestingly enough, if you live near the coast in California, you always have a sweatshirt handy.

In the afternoon, the air almost always has a cool bite to it. On the rare occasion that the sea breeze does not kick in, you definitely notice and it's probably because you are in the middle of a Santa Ana wind event.