The National Weather Service has extended its excessive heat warning for Freeborn County and much of the region through Wednesday.

The agency’s bureau in Chanhassen first issued the warning on early Monday morning, and it had been slated to end Tuesday night. Now it expires at midnight tonight.

Heat index values are forecast to range between 95 and 100 across the southern third of Minnesota, says the warning. The humidity level at 7 a.m. today was 94 percent, with a dew point of 72.

“The prolonged period of heat and humidity has compounded the heat stress on human and animal populations,” the warning states.

It says some relief from the humidity is expected Thursday. The high for air temperature today is forecast at 90 degrees, according to the National Weather Service. It is expected to be 89 Thursday, but not as humid. Friday has a high of 91.

Warm temperatures are forecast to continue through Labor Day weekend.

The warning was extended for Freeborn, Faribault, Waseca, Steele, Martin and Blue Earth counties, as well as counties along the Minnesota River and in the metropolitan Twin Cities. A heat advisory had been in place for Mower, Dodge, Olmsted and Fillmore counties, along with some counties along the Mississippi River, but that came to an end Tuesday night. Those areas are under the scope of the National Weather Service bureau in La Crosse, Wis.

To the west and south, in areas under the scope of bureaus in Sioux Falls, S.D., and Johnston, Iowa, heat advisories are in place. This includes Worth and Winnebago counties in Iowa, where the advisory was in effect until 7 p.m. today. The Johnston bureau states heat index values will reach between 100 and 105 across much of the state.

“The warning is used for conditions posing a threat to life,” states the weather service website. “An advisory is for less serious conditions that cause significant discomfort or inconvenience and, if caution is not taken, could lead to a threat to life.”

The weather service urged people to drink plenty of fluids and avoid strenuous outdoor labor. It says young children or the elderly should remain in an air-conditioned place. It also urges people to check up on relatives, neighbors and pets. Call 911 in the event of a heat stroke.

School starts Tuesday in many districts. The Albert Lea forecast calls for sunny skies and a high of 77 degrees.