Muggy, tropic-like heat has engulfed the Twin Cities, making this week one of the hottest so far this year for the metro area and surrounding communities.

After the heat index hovered in the upper 90s throughout the day Sunday, the National Weather Service issued a heat advisory for the metro through 10 p.m. Monday — only the second such advisory for the area so far this summer. A heat advisory is triggered in the metro when the heat index, or what it feels like to be outside, reaches 90.

“July is overall climate-wise the warmest of the year. We’re still in the warm stretch of summer,” said Tyler Hasenstein, a meteorologist at the Chanhassen office of the National Weather Service (NWS).

The heat index is the combination of dew points, humidity and temperature, meteorologists explained. Sunday’s temperature hit 90 in the metro with dew points reaching the 70s. For residents without air conditioning, there will be no reprieve overnight with temperatures staying in the low and mid-70s.

Those “feels like” readings create an increased risk for heat-related illness for anyone taking on outdoor activities or living with limited or no access to air conditioning, the NWS added.

“Take extra precautions if you work or spend time outside,” the agency’s Monday predawn heat advisory read. “When possible, reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. ... Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency. Call 911.”

So far this summer, the Twin Cities has had three days that have reached the 90s, including Sunday. Typically by this time of year, the metro has recorded five days in the 90s, Hasenstein said.

“We’re behind schedule,” he said.

Even northern Minnesota, which typically has cooler weather, was hot and steamy this weekend.

Brainerd hit 92 on Sunday — a couple degrees hotter than what was recorded in the metro at that time, Hasenstein said.

In the Twin Cities, temperatures are expected to continue to hover in the 90s on Tuesday and Wednesday.

The heat and humidity also ushered in some severe thunderstorms Sunday night across Minnesota.

According to the Weather Service, 2 to 4 inches of rain fell across the central region, creating flash flooding in cities such as Brainerd, where heavy rain opened up a sinkhole on one street, the Brainerd Dispatch said.

A funnel cloud was spotted in Pine River, pea- and quarter-sized hail hammered parts of Hackensack, and downed power lines were reported in Crosslake, according to the NWS. In Little Falls, hail smaller than an inch in diameter was reported as the storm moved east across Minnesota.

In Fergus Falls, the city was struck by wind gusts up to 54 miles per hour and nearly 4 inches of rain, damaging trees and power lines, which caused power outages in some neighborhoods. A flooded street temporarily stranded motorists, but they were able to get to safety and no injuries were reported, said Fergus Falls Police Sgt. Kevin Sonstebo.

“It’s dissipated already,” he said Sunday evening, adding that crews were already making repairs. “Nothing unusual except a good summer storm.”