When will the heat wave on the West Coast end?

The core of the heat battering the Western United States will slowly move inland by mid-September, but it will take until early next week for coastal areas of Southern California to cool, AccuWeather meteorologists say.

The bulge in the jet stream responsible for the heat will collapse this weekend and next week, allowing cooler air to flow in from the Pacific. This will happen first along the Northwest coast this weekend, then south to California, and then inland across the Northwest early next week.

Highs in Seattle will drop to 80 degrees Fahrenheit on Saturday, 70 degrees Fahrenheit Sunday through Monday, and 59 degrees Fahrenheit midweek. Temperatures in Portland, Oregon, will drop more slowly, but highs are expected to be 80 degrees Fahrenheit Saturday through Monday and 70 degrees Fahrenheit for most of the rest of next week.

Further south, downtown San Francisco is not as badly affected by the heat wave and will not experience any significant cooling when the new heat wave sets in. Maximum temperatures will mostly be around 21 degrees Celsius until next week.

Meanwhile, temperatures in downtown Los Angeles reached 102 degrees on Thursday. Highs through Sunday will be between 90 and 100 degrees in the Los Angeles basin. Monday is forecast to remain hot with highs well above 90 degrees before a cooling trend sets in later next week with highs above 80 degrees.

The ongoing heat wave is the worst in Los Angeles in two years and is rated “severe” on the AccuWeather HeatWave Severity Index™.

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In San Diego, highs will remain well above 27 degrees early next week before dropping to 21 degrees by midweek.

Further inland, in California’s Central Valley, highs will range between 35 and 38 degrees Celsius over the weekend before rising to 27 to 35 degrees Celsius next week.

From this weekend through early next week, temperatures will temporarily rise inland in the West, but the actual center of heat will shift from the Plains to the Midwest again next week.

As is often the case in late summer, the combination of heat, dry bushland and sunshine increases the risk of wildfires. Breezes generated by the jet stream can further fan existing flames.

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