Excessive Heat — Chisago, Minnesota

2023-07-27 · Chisago, Minnesota

Event narrative

Warm environmental temperatures in the mid to upper 90s combined with high dewpoint values in the mid 70s, caused high heat indices exceeding 105F for approximately three hours. The ASOS station located at the Rush City Municipal Airport recorded an apparent temperature of 107F at 2:15 PM (CST).

Wider weather episode

Surface temperatures reaching the mid to upper 90's combined with dew points in the 70s and lower 80s allowed for apparent temperatures, or the heat index, to exceed 105F in rural MN counties and 100F for multiple hours in the Twin Cities metropolitan area. Strong ridging aloft was in place over the southwestern U.S. which allowed for seasonally warm high temperatures to be carried east via zonal flow over the Central U.S.

In the lower levels, a surface low over the Dakotas along with transport of gulf moisture from the south allowed for dew point temperatures to remain elevated the night prior to July 27th, despite cloud cover lingering from prior convection over the northern plains. As clouds cleared the next day, daytime heating increased surface temperatures in an already humid air mass, causing heat indices to reach dangerous levels.

Some of the highest heat indices from this event were:

Granite Falls, MN in Yellow Medicine County: 116F

Redwood Falls, MN in Redwood County: 113F

Willmar MN, in Kandiyohi County: 111F

Cambridge, MN in Isanti County: 108F

St. Paul, MN in Ramsey County: 107F

Blaine, MN in Anoka County: 107F

Olivia, MN in Renville County: 107F

Rush City Municipal Airport in Chisago County: 107F

Princeton, MN in Sherburne County: 107F

MSP Int'l Airport in Hennepin County: 103F

Airlake Airport in Dakota County: 101F.

Source: NOAA Storm Events Database, event_id 1107213. Narrative written by the NWS forecast office that issued the report.