Why is there a heatwave on the West Coast?

As of September 5, 2024, a severe heat wave is threatening health and safety across the U.S. West Coast (1)(2).

The heat wave was triggered by dry conditions and typical seasonal weather patterns. September is often an extremely hot month in Southern California, Nevada, and Arizona, as these regions experience dry, desert-like conditions. These weather patterns lead to high-pressure systems that trap heat, creating persistent elevated temperatures.

Heat warnings were also issued for Oregon and Washington, where a September heatwave is more unusual, as cooler Arctic air typically begins to move in by this time of year.

Which cities or areas are affected by the heatwave?

Several major cities are at risk during the sustained heatwave, including:

• Las Vegas
• Los Angeles
• Phoenix
• Portland

Landmarks like Furnace Creek in Death Valley National Park, known for extreme heat, are seeing temperatures climb as high as 120°F.

How long will the heatwave last?

The heatwave began early this week and is expected to last until Friday, September 6, 2024. Temperatures started rising gradually at the beginning of the week and are forecast to peak on Thursday and Friday, with some areas experiencing highs of 100–120°F.

By the weekend, temperatures are expected to begin tapering off, bringing some relief to the affected regions.

Are there any alerts in place?

Several alerts have been issued due to the ongoing heatwave.

An excessive heat warning is in effect for most of Southern California through Friday; only coastal areas are excepted from the warning. The Inland Empire, San Fernando Valley, and other inland locations are seeing the highest temperatures, expected to reach up to 112°F.

The South Coast Air Quality Management District has issued an ozone advisory for regions like the Santa Clarita and San Gabriel Valleys due to elevated smog levels caused by the heat.

The National Weather Service has advised residents to avoid outdoor activities during peak heat hours, check vehicles for children and pets, and stay hydrated. Residents are encouraged to use cooling centers set up across cities like Los Angeles to avoid heat-related illness. Elevated wildfire risks, due to dry, hot conditions, are also being monitored, especially in mountain and desert regions.