Weather News

Is this record-breaking heat the new normal in South Florida? Here’s what experts say

We’re only two and a half weeks into summer, and a common theme of South Florida small talk is “it’s never been this hot.”

Tuesday afternoon’s record-breaking 98 degrees reading beat a 1998 high of 95 in Miami, according to the National Weather Service.

And we’ve been a few degrees above average for weeks now.

So is this just our new normal?

Well, maybe. It turns out, we’re currently in a pattern of high pressure that causes drier air to settle over a region, thus heating the surface, explained Robert Garcia, a meteorologist with the National Weather Service in Miami.

The pattern of easterly trade winds, which helps deliver morning showers in the eastern U.S. and provide some cooling for places like Florida, have been disrupted of late by the lingering high pressure.

In our three-dimensional atmosphere, the high pressure in the upper atmosphere causes the air to sink and compress, which heats up that air. This is why we are feeling the heat.

Trade winds

“Until we set up a normal easterly flow there will be less cloudiness and fewer shows and thunderstorms,” said H. Michael Mogil, a certified consulting meteorologist in Naples.

This stretch of high pressure and its affect on the trade winds could be changing.

“You have patterns and shifts and we are shifting already — you can tell by today being rainier,” Garcia said. “This pattern isn’t that unusual, especially for us in the month of July. Normally, we don’t see record breaking heat each day but it’s not unusual to have high pressure build over us and sit over us for days and cause sea breezes later. In terms of a ‘new normal’ this is not outside our normal.”

But it’s shaping up to be just outside the norm in the last month.

Above average June

The average temperature in June in Miami was 84.8 degrees “and that was running 2.1 degrees above average,” said National Weather Service-Miami meteorologist Paxton Fell.

July is only three days old and its monthly average is usually 88.3. “We are about 4.2 degrees above that, at 92.5 now,” she said.

The July 4th average is 90 and the National Weather Service is forecasting 92 degrees for Thursday.

“It looks like we won’t break records, depending on the cloud cover, but that could change,” Fell said. Heat index readings of 101 to 107 degrees are still likely, the service said in a hazardous weather outlook.

This recent stretch of 90-plus degrees, with triple-digit heat indices, is happening because that lingering high pressure is not giving us the cooling benefits of sea breezes, said Fell.

“In the case of the last few days, a delay in sea breeze development has caused temperatures to soar — as clouds are slower to develop associated with sea breeze — so more sun equals higher actual temps, which in combo with dew points, create triple digit heat indices,” she said.

Relief on the way

Wednesday afternoon already saw a break thanks to a line of strong storms that moved through parts of South Florida, including Kendall and Doral.

Some relief could be on the way later in the week, too.

“High temps look to drop back down to normal beginning around Saturday — upper 80s to low 90s,” Fell said. “Heat indices will be in the upper 90s to low 100s still, however.

That’s because rain could be coming back Friday night into Saturday — a 40% chance on those days. Sunday rain is even more likely at 50%.

Independence Day, however, should be mostly rain-free, at 20%, so aside from sweltering on Thursday, your barbecue or parade plans should be a blast.

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Dashboard readings have topped 100 degrees in Miami in June and so far in July. But the National Weather Service notes these readings aren’t accurate and are affected by many factors, including road heat and proximity to other cars and a car’s color, too. Howard Cohen hcohen@miamiherald.com

Truth about dashboard readings

One thing you can do — beyond the recommended and essential consuming of water to stay hydrated and wearing loose, light-colored clothes and never leaving children or animals sitting in a closed car — is concern yourself less with what your car’s dashboard tells you about the weather outside.

When you see 103 on your dashboard, you immediately feel hotter as if it an actual 103 degree temperature. It’s a false-reading, says the weather service’s Fell. The car’s proximity to the ground and other cars belching heat affects the dashboard thermometer reading.

“Those aren’t accurate. The car is so close to the road and it emits its own form of heat,” she said. “And the car is close to other cars. So those temperatures tend to read higher. It depends on the color, too. Black cars read higher than white cars.”

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Miami Herald Real Time/Breaking News reporter Howard Cohen, a 2017 Media Excellence Awards winner, has covered pop music, theater, health and fitness, obituaries, municipal government and general assignment. He started his career in the Features department at the Miami Herald in 1991.
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