Dr. Robert Rohde

The March heatwave in the USA set many impressive records. 21 weather stations recorded daily temperatures at least 40 °F (22 °C) above normal. For example, Centerville, South Dakota reached 93 °F (34 °C) on a day when the normal high would be 49 °F (9.4 °C).

We need to talk a bit about how utterly absurd the March heatwave was in the USA. This heatwave would have been impossible without a boost from climate change, but even with climate change it remains a deeply unlikely event. A thread looking at some of the numbers. 🧵

To begin, let's look at monthly mean temperature. The March average temperature across the Western USA was about +11.6 °F (+6.4 °C) warmer than the mid-20th century average. That's an absurd 3.6 °F (2.0 °C) higher than the previous record. 2/

As is common with heatwaves, warmth in one area was balanced against relative cooling in other areas. In this case, cooling occurred over Canada and Alaska. This also included some local record lows, though not as extensive or extreme as the highs observed in the USA. 15/

To begin, let's look at monthly mean temperature. The March average temperature across the Western USA was about +11.6 °F (+6.4 °C) warmer than the mid-20th century average. That's an absurd 3.6 °F (2.0 °C) higher than the previous record. 2/