So long cool and comfortable; hello hot and juicy air.

Thunderstorms that rolled through the metro area and dropped hail as large as Ping-Pong and tennis balls in a few locations early Thursday ushered in the leading edge of heat and humidity that will make the weekend feel tropical.

Temperatures in the low to mid-90s combined with lots of moisture in the air will make it feel like it’s closer to 100 degrees Friday through Sunday before slightly cooler and drier air begins to filter in, said National Weather Service Meteorologist Chris Franks.

The mercury could climb into the upper 90s in southwestern Minnesota, Franks said.

The arrival of the hot and heavy air is a tad early, but not uncommon for the second weekend of June.

“It’s more common in July,” Franks said. “It’s hard to go a summer without it. But here we don’t get heat indexes between 95 and 100 on a week by week basis. It’s around for a few days, then goes away. It will be warm and juicy.”

Heat indexes — summer’s version of windchill — pinpoint what it will feel like outdoors. They are expected to be highest between Friday night and Saturday afternoon, Franks said.

Coinciding with the arrival of the most uncomfortable air of the season, lifeguards go on duty Saturday at beaches and pools operated by the Minneapolis Park and Recreation Board. Swimming areas, expected to be packed, officially are open during park hours even if a lifeguard is not on duty.

St. Paul’s Lake Phalen beach, the Highland Park Aquatics Center and Como Park Regional Pool all open Saturday, while the Bunker Hills Water Park in Coon Rapids opens Friday.

Thursday’s storms dropped 2.73 inches of rain in Carver while more than 2 inches in places such as Chanhassen, Victoria and Bloomington. Ping-pong ball-sized hail fell in Burnsville, Chaska and Shakopee and stones as big as tennis balls were reported near Watertown. A few trees were felled in Wright and Scott counties, the weather service said.

By Tuesday, temperatures are forecast to return to the 70s with a chance of rain each day Sunday through Wednesday.