Fort Myers, Naples heat index will be in triple digits. How long will excessive heat last?

Peak summer conditions are upon us as another heat advisory was issued Tuesday for parts of Southwest Florida.

Heat index numbers this week will range from 100 to 112 in Lee and Collier counties, according to the National Weather Service.

Daily highs are running a few degrees below record levels, but overnight lows are only dipping to around 80 degrees, while humidity levels are rocketing to 80% and above.

The muggy conditions make it feel as though temperatures are at an all-time high because sweating is not effective when humidity levels are high.

A ridge of high pressure is sitting over the state now, keeping skies clear long enough to create intense heat.

"The average high for this time of year in the past 30 years is 92, and it stays at that for the rest of the month," said Jennifer Hubbard, a meteorologist with the NWS in Ruskin, which covers the Fort Myers-Lee County area. "It's 94 today so we're a few degrees above that."

The heat may feel remarkable, but it's only a few degrees above average, according to records.

"Records range from 96 degrees on the 18th and 24th to 101 degrees on the 20th, and that is the highest for the month, tied with the 7th and both occurred in 1942," Hubbard said.

Hubbard said Saharan dust from Africa last week kept thunderstorm activity at bay which allowed for daily highs to peak.

Overall, conditions get hot in Florida, but not as hot as many other regions in the United States.

Being surrounded by the Atlantic Ocean and Gulf of Mexico moderates high temperatures as sea breezes and thunderstorms routinely cool off the Sunshine State during the oppressive summer months.

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Heat index will be in the triple digits all week

"The sea breeze helps bring in cooler air from the Gulf in the coastal areas, and that keeps the coastal areas cooler, and the thunderstorms keep the inland areas cooler," Hubbard said. "When we don't get those thunderstorms, that's when we see those heat advisories. When you see high temperatures in New England and the heartland, it's usually because there's a big dome of high pressure and you don't get a lot of cloud cover or anything to cool off or suppress those conditions."

She said the heat index in Lee County will vary from 100 to 105 degrees.

"There's a pocket of dry air moving over the state and the farther south you go, you get hotter," Hubbard said. "Lee County will be close but not quite to the heat index advisory level."

Hubbard said a heat advisory is issued when heat index numbers are expected to be between 108 and 112 degrees. At a 113-degree heat index, an excessive heat warning is issued.

Naples and the Collier County area were under a heat advisory Tuesday

"For Collier County, when the heat index is forecast to be 108 degrees or higher for two or more hours, that triggers a heat advisory," said Robert Garcia, a meteorologist with the NWS in Miami, which covers the Naples-Collier County area. "We're forecasting heat index values between 107 and 112."

Garcia advised people to take breaks from the heat if they must be outside during the middle of the day. Stay hydrated, he said, and check in on friends and relatives to make sure they're staying cool.

"The wind is fairly light, and it feels like it's oppressive out there," Garcia said. "The idea is when you have these hot temperatures and high humidities. heat illnesses are much more likely for the elderly and people who are working outdoors. You're starting to get out of normal Florida days and into days that are particularly stifling."

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Garcia said Saharan dust may move back over the state later this week.

Hubbard said the typical afternoon thunderstorms and sea breeze-driven weather would help conditions now.

"We have a ridge of high pressure and that will keep southeast winds in place, and that allows for higher rain chance in the afternoon and evenings," Hubbard said. "So we're going to get nice and hot prior to the storm and the afternoon and evening is when they'll move through and cool us off."

This article originally appeared on Fort Myers News-Press: Fort Myers, Naples heat index will be in triple digits. How long will excessive heat last?