St. Cloud, MN Weather Forecast

Even More Humid Than Previously Expected

So far, the humidity has been even worse than forecast. Temperatures got the hottest from the Dakotas to northern Minnesota (see area of black turn to white each afternoon on the College of DuPage continental US clean infrared satellite loop). In north central and northwestern Minnesota, high temperatures got to the upper 90's, as expected (see yesterday's 4 PM NWS WPC North America zoom-in map) with 100's in the Dakotas. International Falls hit 98 degrees, breaking a record high. However, dew points remained in the Florida-like low to middle 70's (see numbers at lower left on the NWS Aviation Weather Center METAR map) during the afternoon (19Z-23Z). That again allowed heat indices to reach the 100's from Fergus Falls northward (set time to 3-5 PM on the NWS Minnesota hourly weather round-up). In central Minnesota, the dew points hung around 70. The extra moisture took some of the sun's heat out on the way down, so high temperatures only made it to the lower 90's with heat indices in the upper 90's to near 100.

During the overnight hours, when the winds lighten near the ground, the mature stage of the corn crop is helping to push dew points into the oppressive middle 70's (see dark orange on the UCAR hourly dew point chart), about as bad as humidity typically gets in Florida. That will again help to hold overnight temperatures up (see latest NWS Aviation Weather Center METAR map), making it harder for people without access to air conditioning to cool off. 

Intense Heat and Humidity Today and Tomorrow

The outlook for this week continues to be about the same as we will remain in the same air mass through at least Thursday. I am dropping high temperatures slightly to account for the persistent oppressive humidity. So, I think central Minnesota will tend to see highs in the lower rather than the middle 90's. The hottest air will remain in northwestern Minnesota today into tomorrow, so those area could see highs in the upper 90's with perhaps a few 100's (see reds and purples on the NWS Heat Risk forecast). In central Minnesota, the higher humidity will likely top out near or just above 90. You can find the latest temperatures and dew points on the NWS Aviation Weather Center METAR map and the same information plus the latest heat index, when it climbs to 88 or higher on the NWS Minnesota hourly weather round-up.

The National Weather Service again has an extreme heat warning, this time for all of Minnesota from the Red River Valley and the Canadian border to the Minnesota River Valley and Red Wing.

The warning is in effect from now all the way through 9 PM Thursday in central Minnesota and the Minnesota River Valley. This warning lasts until 1 AM tonight in northwestern Minnesota and until 7 PM Tuesday in northeastern Minnesota. There is increased danger, both since much of northern Minnesota doesn't have cooling shelters, and there is no refuge while camping or canoeing. The danger is also higher in central Minnesota, because anyone without air conditioning will face several nights with lows at least in the 70's. So, it will be important to check on vulnerable people throughout this outbreak. 

Here are the safety steps for intense heat and how to protect residents from overexposure to the sun. Here is a link to the Mayo Clinic's heat awareness page. This weather produces more deaths than any other weather-related phenomenon in the US. 

If you're in northern Minnesota where air conditioning is harder to find, or camping, it would be a good idea to change your plans to take advantage of somewhere cooler.

Wildfires Expand With More Fires Likely Today

There is also a red flag warning, the highest category of fire danger, in northeastern Minnesota (you can't see it on the NWS Duluth watch-warning map because these areas also have the extreme heat warning). The heat will be combined with slightly stronger southwest winds today.

The wildfires have spread through a larger area in northeastern Minnesota during the past day, so the emergency conditions continue.

The Minnesota Department of Natural Resources has banned campfires in forested areas of Cook, Lake, and northern St. Louis Counties and has restricted fireworks. Several entrances to the Boundary Waters Canoe Area Wilderness were closed due to the wildfires burning. And the ban on campfires has been put up again.

Slightly Less Humid Mid-Week? 

On Wednesday, the hottest and most humid air will be pushed to our south and west by a weak front. I don't have a great chance for showers and thunderstorms, because we will still have a plume of very warm air aloft that will keep many thunderstorms from developing. However, this system will allow air from the southern Canadian Prairie Provinces to move in. That air will be slightly less humid than what we have now, so dew points will fall back into the upper 60's. However, that will give us a better chance at highs in the middle 90's Wednesday through Friday, depending on how sunny we can remain.

That sunshine might be cut down a bit by smoke either from the northern Rockies fires or the fires in the northern Prairie Provinces (see EPA fire and smoke map).

The reason for the extreme heat warnings expiring in northern Minnesota sometime on Tuesday is that forecasters are uncertain whether high temperatures may fall back to the 80's on Wednesday and perhaps Thursday. However, if we keep the hot air with only slightly drier dew points, at least heat advisories will be needed. There is also the chance in northeastern Minnesota of east to northeast winds which would allow the air cooled over Lake Superior to move in.

Weekend Best Chance for Relief (But Uncertain How Much)

The first chance of true relief (getting highs out of the 85-95 range, getting lows into at least the lower half of the 60's) would be over the weekend, but the computer forecasts are inconsistent about the potential low pressure system and track that would be able to bring in air from the central or northern Prairie Provinces. So, I would guess for now that the heat won't be as intense this weekend, but I can't say how cool or dry it would be. 

The cold front on Friday might bring a better chance of showers and thunderstorms on Friday or Friday night, but I still don't have any better than a 1 in 3 chance for storms even then.