Are California’s Heatwaves Getting Worse?

By Paul Homewood



California is supposed to be experiencing a record heatwave, of which Death Valley is just one example.



Naturally the likes of the Guardian only want to tell you about temperatures in big cities or the airport at Stockton:



But what do stations relatively unaffected by UHI tell us?

Four years ago I analysed nine long term, high quality USHCN sites, none of which showed any upward trend in summer high temperatures. They pretty much cover all of California, so should give a good representation of the state as a whole. One incidentally was Lemon Cove, which I used as an example this week.

Below are CLIMOD charts for the others, showing the highest temperature recorded each summer. They range broadly from north to south, with Orland, for instance, north of Sacramento, and Redlands down towards Palm Springs. One station, Davis, has no data on CLIMOD.

Underneath each chart is the highest temperature recorded this week, though some stations have not been updated yet – If I remember, I’ll update next month!



Aug 2020 max – 108F




Aug 2020 max – 110F




Aug 2020 max – 112F



Aug 2020 max – 109F





In no case is this week’s peak temperature, where available, in any way unusual. Nor have  summer high temperatures been trending upwards.

I have just one more chart to show you, and I’ll use Lemon Cove again. This one plots the number of days above 100F each year:


We can see a gradual rise from the 1960s, but recent years still don’t hit the peaks seen in the 1930s and 40s.

This is a good indicator of the duration of heat waves, and along with the summer high temperature data shows that heatwaves in California are no more severe than they have been in the past.


August 20, 2020 at 12:42PM

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