St. Cloud, MN Weather Forecast

Air Quality Alert Through 11 AM Friday

The worst impacts of all of the weather issues facing Minnesota is now the extremely poor air quality in eastern and central Minnesota. The dense smoke from the northeastern Minnesota wildfires pushed south and southwestward during yesterday (push loop and set for northern US on the EPA AirNow interactive AQI map). Click on the hourly time series, PM 2.5 for pollutant, and St. Cloud to see the first surge of pollution after 10 AM and the huge jump from 2 PM on. You can also see the milky white smoke plume on the College of DuPage north central US visible satellite (veggie blue) loop when you set the frames to show yesterday afternoon)

Within those areas ranked maroon, the Minnesota AQI has ranged from the 300's to the 600's, setting records for the worst air quality in Minnesota history. Just for some perspective, I've previous seen this kind of poor air quality in China before they made a major push to clean their smog in the 1990's or in Mongolia (or of course right in the midst of an intense wildfire). 

At these ratings, eyes water after about a minute of exposure and heart and breathing problems can develop quickly. And that's true for everybody (scroll down to see description of maroon air quality on the Minnesota Pollution Control Agency air quality alert message). So, we should avoid being outdoors and running gas powered engines as much as possible. The air quality alert continues through tomorrow and areas with concerning pollution levels have been expanded to the Red River and Minnesota River Valleys.

Safe to Go Out Again? Maybe Friday PM (Another Smoke Surge Friday Night?)

When will this ease? The worst of the air pollution may move eastward this afternoon or tonight, but the levels should still cause problems for everyone. True relief won't come until at least Friday if some thunderstorms develop and that chance isn't terrific (see discussion below). There might be some small relief as our airflow changes to southwest-to-northeast on Friday (see forecast smoke plume from firesmoke.ca). On Friday night, a cold front will push through with a small chance for showers and thunderstorms, which could help ease the smoke. That will also change our winds flow to the northwest. That will eventually bring cleaner air from the Canadian Prairie Provinces, but note that the forecast smoke plume from firesmoke.ca is blowing higher density smoke that will be in southern Manitoba and far western Ontario. So, we could have Friday night and Saturday morning problems as well.

In the long run, there are many wildfires burning from the Yukon and Nunavut into the northern Canadian Prairie Provinces, so I'll be watching air quality for several days to come. 

The wildfires continue to burn in north central and northeastern Minnesota near the Canadian border as well as much of far western Ontario. That has allowed the dense smoke to move into Wisconsin and the Michigan Upper Peninsula. The smoke will be headed towards New York and New England.

Smoke Particles Will Ease Heat Slightly, Especially Today

The advance of the thick smoke cut down on high temperatures quite a bit, since smoke particles reflect some of the sun's energy back to space. Temperatures at 3-5 PM (20-22Z on the NWS Aviation Weather Center METAR map) got to the upper 80's in central Minnesota, but only the low to middle 80's to our northeast and to the 70's in northeastern Minnesota. The Twin Cities did get most of the daily sunshine before the smoke moved in. The combination of 90-95 degree highs and dew points near or above 70 pushed the heat indices to near or above 100 degrees again (set time to 3-5 PM on the NWS Minnesota hourly weather round-up).

St. Cloud did reach 91 degrees before the dense smoke moved in (see NWS: last 72 hours of St. Cloud observations) with a heat index of 95 at 2 PM. That makes 4 straight days with at least a 90-degree high, St. Cloud's longest heat wave since July 25-28, 2023. St. Cloud's most recent 5-day heat wave happened one month earlier (June 19-23). There were 24 days with a high of at least 90 degrees in 2023. The record for consecutive 90-degree highs was during that July 1936 heat wave I've hyped so much recently (on NWS Twin Cities NOWdata, select St. Cloud area, daily summary for a month, and 1936-07). There were 14 straight days with a high of at least 90 from July 5 through 18.

Behind the weak cold front, we will see slightly cooler and merely uncomfortably humid air. There is the potential for the front to push northward again into southern and central Minnesota tomorrow. The southwest winds might temporarily ease the smoke issues, but that is uncertain (depends on how far south the smoke gets today). I have highs in the 80's today, breaking the heat wave in St. Cloud, although the Twin Cities could brush 90.

Warmer and More Humid Tomorrow, Uncertain How Much Smoke

We might hit 90 again tomorrow with dew points back in the Florida-like 70's, so another heat advisory could go out for tomorrow, but only the Twin Cities Metro area continues in the extreme heat warning, now today through Friday evening. See the NWS Minnesota hourly weather round-up for the latest temperatures, dew points, and heat index.

Thunderstorm Chances Small, Except Northern MN and They May Not Help

There will be small chances for showers and thunderstorms, with the best chance in northern Minnesota, both when the front pushes northward tonight into tomorrow morning and when the stronger cold front pushes to near the Minnesota-Iowa border by Saturday morning. That's when some of the moisture that has fueled Intermountain Region thunderstorms (see College of DuPage continental US radar loop) could stream eastward into a low in the Canadian Prairie Provinces. There is even a low risk of severe storms tonight in northwestern Minnesota eastward to International Falls. That risk moves to northeastern Minnesota for the late Friday storms.

Still, any thunderstorms will be fighting the very warm air aloft. And, any lingering smoke will cut down on ground heating, so the areas seeing the required 80 degree difference between the lower atmosphere and about 5 miles up will be limited. Northern Minnesota (see Days 1-2 on the NWS WPC quantitative precipitation forecast) will have a better chance for these storms than central and southern Minnesota. I only have a 1 in 5 shot at showers and thunderstorms in St. Cloud early tomorrow and Friday evening.

The worst case scenario is that the thunderstorms are relatively high in the lower atmosphere, producing little rain, but with lightning strikes that could touch off more wildfires. The fire danger category is a little lower, since the cooler temperatures are expected, but it could creep up again tomorrow.

Saturday Cooler and Less Humid, But Potential for Another Smoke Round

Saturday's high should be cooler thanks to the Canadian air, but we could get a recycled push of the current smoke plume before it moves southeastward later. So, I have highs back in the 80's.

Another low pressure system will whizz by to our north Sunday night. That will bring another cycle of being warmer and more humid on Sunday, but bringing at least drier air in for Monday. The rain chances with this front are iffy (see Days 4-5 on the NWS WPC quantitative precipitation forecast) with the best chance on Sunday night when the cold front goes through. Sunday's highs will depend on whether we have either some lingering smoke or dew points charge upward into the 70's. Either one of those factors would make it hard to reach a 90 degree high. I have a range from the middle 80's to 90.

Drier Canadian Air Early Next Week, But Will Heat Linger Monday and Smoke Arrive Sometime During the Week?

The long-promised break in our steam bath is the cooler air behind Sunday's front. The computer forecasts have been switching around about how cool the air will get behind the front. The latest information drops the humidity Sunday night into Monday, but keeps us not far to the north of the front. Some of the computer forecasts are trying to make Monday as hot as tomorrow (and hotter than Sunday). However, the key to this forecast will be how quickly any smoke from the many wildfires burning from the Yukon and Nunavut into the northern Canadian Prairie Provinces get here. I have basically punted on Monday's high (somewhere between 85 and 95).

The latest information has the cooler part of the Canadian air arriving during the middle of next week. Again, the potential for wildfire smoke, even if it doesn't get to the ground, cutting down high temperatures makes a temperature forecast uncertain. There could also be some small, but uncertain chances for thunderstorms. But, we are likely to see the conditions in Minnesota worsen when the new US Drought Monitor comes out today and it will get even worse over the next week. 

When we aren't warning heavy, I will get back to how we haven't made up for last fall's low rainfall.