Record Nighttime High Temperatures Bigger Deal For Health, Crops, Climate Than Daytime Highs
We've written about this one a number of time previously, but it bears repeating: Though there have been plenty of record high daytime temperatures set in this most recent heatwave, perhaps the more interesting and more dangerous trend (on many levels) is that nighttime temperatures aren't cooling off as much.
As New York Times reports today, so far in July 12 weather stations in the US have recorded all-time daytime highs, but 93 have recorded all-time nighttime highs.
Last year for the entire summer, 37 states set high nighttime temperature records, with half of all US weather stations recording top-five record nighttime highs.
NYT sums up well the immediately deadly implications of nights not cooling off that much:
Studies suggest that kind of exposure to high temperatures increases the risk of death for vulnerable groups like the elderly, said Rebecca Noe, an epidemiologist at the Center for Disease Control and Prevention. The agency's study of a 2005 heat have in Maricopa County, Ariz., found that elderly people were more likely to die indoors, while those who died outside were more likely to be younger, working in outdoor occupations or homeless.
In the recent deaths of upwards of 1500 cattle in South Dakota, high nighttime temperatures was cited as a contribution factor.
Longer term, high nighttime temperatures have been shown, at least with rice crops, to have a bigger impact on crop yields than increases in daytime temperatures--for each 1°C increase in nighttime temperature above the long term average, a 10% decrease in crop yield was observed.
Other crops can be affected as well. Last year the lack of usual cooling at night led to nearly the entire loss of the northern Alabama apple crop, as the trees prioritized "short growth at the expense of fruit growth."