Speaking of warm nights, the United States had something for the history books last month.
Forecasters said that in July, the US mainland set a record overnight heat, providing little respite from the heat of the day for people, animals, plants and the power grid.
The average low temperature in July in the lower 48 states was 63.6 degrees Fahrenheit (17.6 degrees Celsius), surpassing the previous record set in 2011 by a few hundredths of a degree.
The mark represents not only the warmest overnight average for July, but for any month in 128 years of record-keeping, said Karin Gleeson, a climatologist at the National Oceanic and Atmospheric Administration (NOAA). July’s minimum temperature was more than 3 degrees Fahrenheit (1.7 degrees Celsius) warmer than the average recorded in the 20th century.
Scientists have long pointed out that night temperature is important for health.
Gleason said, “When temperatures reach highs or near record highs during the day and there is no overnight improvement with cold weather, it puts a lot of pressure on plants, animals and humans.” ” Friday. “It’s no small thing.”
In Texas, where the monthly average daytime high was above 100 °F (37.8 °C) for the first time in July, causing the power grid to be overwhelmed by heavy use of air conditioners, the night average temperature was 23.5 °C (74.3 °C). F) was. ), which is 2.2 °C (4 °F) higher than the 20th century average.
Over the past 30 years, nighttime lows in the United States have increased by an average of 1.2 °C (2.1 °F), while daytime highs have increased by 1.1 °C (1.9 °F).
Climatologists have said for decades that global warming caused by the burning of coal, oil and natural gas will accelerate the warming of the world at night and in the north polar regions. A study this week indicates that the Arctic is warming up to four times faster than the rest of the planet.
Nights heat up faster because daytime warming helps the air hold more moisture, and then that moisture helps to trap heat throughout the night, Gleeson explained.
On Friday, NOAA also released global temperature data for July, showing that it was the sixth warmest month on record, with an average temperature of 16.67 °C (61.97 °F) versus 0.87 °C (1.57 °F). ) Is. ) warmer than the 20th century average. It was the month of heat waves, with the UK breaking its all-time heat record.
Seth Borenstein is on Twitter: @borenbears
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