Why it’s not as cold as forecast, but arctic air still on the way

South Florida’s low temperatures didn’t dip as low as was expected, hitting 52 degrees this morning in West Palm Beach and 53 in Fort Lauderdale.

Broward County was so concerned about overnight lows in the 40s, it opened emergency shelters yesterday.

But a broken layer of clouds curbed cooling early this morning and, in general, temperatures just have not fallen as low as expected. (More on why that is later.)


Overnight temperatures for Wednesday.

However, as another surge of cool, dry air makes its way through South Florida today, temperatures will not warm much more than the low 60s and the coldest night is expected to be tonight through Thursday morning.

Big jet of arctic air is blasting down through the center of the country, pushing more frigid air toward the south

Big jet of arctic air is blasting down through the center of the country, pushing more frigid air toward the south

“Can’t rule out some patchy frost in the Glades,” forecasters in Miami wrote this morning. “But confidence in this is low.”

The overnight low tonight could hit 41 degrees in West Palm Beach, which would be the coldest ambient temperature this month, but still not as cold as the 40 degrees the region saw January 24.

February temperatures

February temperatures

More northern and interior areas of Palm Beach County may dip into the upper 30s. Wind speeds are expected to be much lower than originally thought, so wind chill shouldn’t be as a big issue.

Thursday could warm up to 65 degrees with temperatures possibly in the low 70s Friday.

Remember, the normal daytime high for this time in February in South Florida is 76, with a low of 59.

Still, we’re unlikely to break any record overnight lows. In 1900, the temperature went to 34 degrees on Feb. 10.

So, why do the clouds make for a warmer overnight? It’s not because they’re acting as “blankets” for the Earth.

According to professor’s at Penn State University’s Department of Meteorology, clouds are more like heaters.

Here’s why: The atmosphere is constantly emitting infrared radiation. In fact, the atmosphere, on average, sends at least a comparable amount of infrared radiation to Earth as the sun because the sun only shines for a limited time and occupies much less of the sky than the atmosphere.

While clouds can limit solar radiation from reaching the earth – why it’s cooler on a cloudy day – they actually increase downwelling radiation and emit their own radiation.

“In this light, think of clouds as space heaters, emitting energy toward the ground,” writes David Babb, a professor in Penn State’s meteorology department. “This is the reason a cloudy night will tend to me much warmer than a clear night.”

For more on how this works, click here. 

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