Believing heat records and not your local microclimate

Record-breaking heat waves are plaguing both coasts, but for swaths of people experiencing less intense heat, "perception versus reality" may be misaligned. In the Southwest, multiple inland areas broke all-time records, while densely populated coastal cities were simply hot, said UCLA climate scientist Daniel Swain in a live briefing delivered Wednesday evening. While much of the East Coast also sweltered, the central U.S. was ever so slightly cooler than average - "and this has been a recurring theme in recent decades," Swain noted.

Excerpts and timecodes from Swain's discussion of extreme heat and wildfires are below, along with more discussion about another series of heat waves coming to the Southwest, how a reprieve in the heat could worsen wildfires, and why an increase in Weather Service heat and fire warnings isn't just because of climate change.

• Is it even hot if YOU can't feel the heat: "Something like 90% to 95% of the land area of California probably saw its hottest mid-June to mid-July period on record - and perhaps more than half of the state's population living in these densely populated coastal zones did not. So, really interesting questions here about the perception of reality versus reality itself."

• Heat records broken in Calif.: "I assure you, it really has been damn hot inland, and record hot … A lot of parts of the Central Valley broke all-time records for the most number of 100- or 105- or 110-degree days, as the case may be in particular locations, in a single month or in a consecutive period. Some places actually saw their singularly hottest day on record. That's a pretty unambiguous statistic."

• Dangerous overnight highs mid-June to mid-July: "Virtually all of California, and now virtually all of Arizona and New Mexico, and now also parts of Colorado, Utah, Nevada and Oregon, all saw a record warm overnight temperatures for this 30-day period. So it's certainly true that it's been hot during the daytime, but it's been even more anomalously warm at night."

• East Coast record heat: "Much of the eastern seaboard of the U.S. also experienced its warmest 30-day mid-June to mid-July period on record just now. The one part of the country that did not, and this has been a recurring theme in recent decades, is the central U.S."

• The Central U.S. "outlier": "The U.S. Great Plains is one of the only places that saw even slightly cooler-than-average temperatures this summer so far, and they have been surrounded by regions that have seen all-time record warmth on all sides, so definitely an outlier there. …It is striking that this region continues to see less summer warming than most other places. Lots of research on that, and some of it may have to do with the fact, frankly, that we majorly irrigate a lot of the central plains at vast scales."

• For a change, natural ignitions driving California wildfires: "There are a number of very active wildfires in California right now. Most of them are relatively far from large population centers, but they're burning in fairly remote, densely vegetated, and in some cases, heavily forested areas, and so these are likely to persist for quite some time. Unlike some wildfire outbreaks now, most of the fires that are currently burning were actually started by natural causes: lightning. So in most cases, these were not accidental human sparks, as is the most common for wildfires sparked in California."

Swain is a climate scientist and researcher with UCLA's Institute of the Environment and Sustainability. View the full, on-the-record conversation online. Media are encouraged to to quote from his comments, reach out to be alerted about Swain's future "Office Hour" Q&As, or get in touch for more insights from him and other UCLA experts.

Alison Hewitt
Senior Media Relations Officer
UCLA Strategic Communications | Office of Media Relations
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