The US Annual Heat Wave Index measures the frequency and widespread nature of heat waves (defined as periods of at least 4 days where average temperatures are extremely rare, expected once every 10 years historically).

It shows clear peaks in the 1930s—especially 1934 and 1936—far higher than recent values. Extended periods of very high temperatures were more common then than in the 2000s–2020s.

The index spiked dramatically during the Dust Bowl due to prolonged drought, poor land management, and natural variability (e.g., ocean patterns like the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation amplifying dry, hot conditions).

Many sources, including NOAA-derived charts, confirm the 1930s stand out as the most extreme for this metric over the full record since 1895.

From NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

There were a few days of hot weather in the US a couple of weeks ago. Attribution “scientists” immediately jumped up and announced that the heatwave would have been “virtually impossible” without challenge.

It’s the same old, unsubstantiated claim that gets wheeled out every time it gets hot. And every time they ignore the lessons of history.

If heatwaves are caused by global warming, what caused them in the past? Not only have they always occurred, they were considerably more severe in the past in the US.

In 2017,  the US Global Change Research Program published the Fourth National Climate Assessment, a report mandated by Congress:

Running to 400+ pages, it was an extremely detailed, fully referenced assessment of the US climate and how it had changed over the years. Chapter 6, “Temperature Changes in the United States”, included this section on temperature extremes:

The evidence was unarguable. By all measures, heatwaves in most of the country, with the exception of the west, had been considerably more severe in the past.

Conversely the same was true of extreme cold – that too had been more severe in the past.

Bear in mind that we are not talking about an isolated phenomenon, the Mid-West dustbowl years. The heatwaves of the 1930s were a national event, not a regional one, and were not confined to one summer. Indeed the heatwaves of the 1910s, 1920s, 1950s and 1980s were all memorable.

These findings were embarrassing to say the least. I recall at the time an attempt to bury them by excluding them from the Executive Summary.

That was in 1917. Six years later, the next edition, the Fifth National Climate Assessment came out with the same message:

Heatwaves had lessened in severity, except in the west. At the same time, cold extremes had also declined, alongside an apparent warming trend at night.

These two reports are now buried in the archives. They are no longer available from the usual public sources.

Thanks to my old links and Wayback though, I have now managed to download both from the NOAA Institutional Repository.