The first day of summer Tuesday came with a warning to stay indoors from the National Weather Service, but the heat advisory is expected to be called off today -- even though it might not feel like it.
High temperatures and a sea breeze bringing more humid air produced dangerous heat index values of 111 degrees Tuesday in Beaufort County, according to weather service meteorologist Aaron Mayhew in Charleston.
Those readings weren't quite as high as in the Charleston area, where temperatures broke or tied records, hitting 102 degrees at the airport on both Monday and Tuesday.
Nonetheless, Beaufort's numbers were high enough to prompt a warning to keep out of the sun from noon to 8 p.m. Temperatures at Marine Corps Air Station Beaufort reached 100 degrees Tuesday, weather service meteorologist Peter Mohlin said.
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Emergency room personnel at Beaufort Memorial Hospital and Hilton Head Hospital reported no patients with heat-related illnesses Tuesday.
The county's heat index is expected to reach 105 degrees today, Mohlin said. Mohlin said it's a "marginal" possibility the county could have another heat advisory, which is when the heat index reaches 105 degrees or higher for two hours or more.
"It's going to be hot no matter what," Mohlin said.
Thursday is expected to be slightly cooler, with highs around 90 degrees and a heat index of 101 degrees.
Beaufort Memorial's assistant emergency room director Ashley Hildreth cautioned residents to stay in air-conditioned places and, if they had to work outside, to stay hydrated and take multiple breaks.
Seeing spots, feeling dizzy or becoming nauseous are signs to go inside and seek further medical attention if the symptoms worsen, Hildreth said.
Children and the elderly are most susceptible to heat-related illnesses, as are those with chronic diseases or altered mental status.
Hildreth said parents should keep an eye on children playing outside and check on older people, as both groups are less able to regulate their body temperatures.
The (Charleston) Post & Courier contributed to this report. Follow reporter Allison Stice at twitter.com/blufftonblogip.