SAVANNAH, Ga. (AP) — The unofficial start of summer feels more like its blistering peak in parts of the Deep South, where temperatures at or near 100 degrees are setting heat records during the Memorial Day weekend.

Heat and humidity were forecast to combine for a dangerous heat index of 105 degrees Fahrenheit on Sunday across roughly 20 counties in southeastern Georgia and South Carolina, said Emily McGraw, a National Weather Service meteorologist in Charleston, South Carolina.

The weather service issued a similar heat advisory for a portion of the Florida Panhandle. McGraw said the forecast showed little relief in sight, and there was potential for some cities to see their hottest days ever in the month of May. Savannah reached 100 degrees Saturday, tying a record and marking the coastal Georgia city’s earliest triple-degree day since 1953. Columbia, South Carolina, on Saturday also hit 100, just one degree shy of a record from 2000.