Photo: Climate Central
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Visitors to San Francisco during the summer typically have the same burning question: “Why is it so cold?”
But those who call the city home may have a differing opinion about the weather. Do you find yourself wearing your fleece hoodie less than you expected? Are you often wishing you had rented an apartment with A/C? Do you read reports of record-breaking temperatures and grumble, “Not again”?
If it feels warmer in the city, it’s not just in your head. Summer nights are getting hotter in San Francisco.
A recent analysis by Climate Central shows summer nighttime temperatures are on the rise in San Francisco. The nonprofit organization, consisting of meteorologists and climate scientists, examined government data to chart temperature trends for more than 200 areas during the summertime from 1970 to 2018.
Their findings for San Francisco reveal a long-term warming trend, with an increase in overnight temperatures by 3 degrees on average.
Spencer Tangen, a meteorologist with the National Weather Service, found similar numbers as the group.
“In the 1970s, the average low temperature was around 53.5 degrees. Now it’s around 56.2 degrees,” he confirmed.
The trend in San Francisco follows warming patterns nationwide, as reported by Climate Central’s recent publication. Reno, Nev. was the highest on the list with an increase of an average 16.9 degrees. Las Vegas trailed behind with temperatures rising by 9.1 degrees.
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While 3 degrees may not seem as dramatic when compared to other regions, even the smallest change can have a significant impact.
“Even if you have a small increase in the average, you have a proportional increase in the extremes,” explained Sean Sublette, a meteorologist at Climate Central.
“A temperature that might have only dropped below 60 once a year, might happen a few times a year — those are the types of extremes that begin to increase,” he elaborated.
Some long-time locals may point out that the city doesn’t warm until the fall months. But Sublette ran the figures for September and October and reported consistent findings: a change from 51.3 to 55.9 degrees.
What’s the reason behind the rise? Of course, it’s the usual suspect: overall global warming due to the burning of fossil fuels. But Sublette offered an additional source for the hot weather.
“Another component is land use or the urban heat effect,” he said. This is the phenomenon where cities are warmer than their surroundings due to the loss of vegetation and addition of paved surfaces.
Even though the change in temperature appears moderate, it is nonetheless moving in an upward direction.
“From year to year, it’s so gradual, most people won’t notice,” said Sublette. “But people who’ve been around for 40, 50, 60 years will probably notice a difference since their childhood.”
Nikki Tran is an SFGATE intern. Email: firstname.lastname@example.org