Wednesday, July 2, 2025  2:45 AM 

Prepared by Bob Weisman, SCSU Meteorologist and Professor Emeritus

Minnesota May Soon Catch a Taste of the Mexican Monsoon

Weren't The Geography Questions Rated the Toughest On 'Are You Smarter Than a 5th Grader?'

You may remember from geography something about the monsoon weather that dominates southern and southeastern Asia (way too much information from this geodiode textbook copy). Since news stories tend to talk about this during the very wet summer months in India, Pakistan, and Indochina (8-12 inches average over all of India with more than 25 inches, green or blue on this map--select normal rainfall and states, 1 mm=.25 inches, so 1000 mm is 25 inches). we tend to think monsoon means rainy season. However, the geodiode textbook copy shows that the word actually means a wind that changes with the season. During the winter, the Asian winds blow from a Siberian high pressure, so the air over India is extremely dry, blowing from the Himalayas, the world's highest mountains out into the Indian Ocean. India tends to have a very dry cold season. However, the circulation reverses during the summer as south winds blow very warm and sticky air from the Indian Ocean over southern Asia. That air is, in turn, lifted along the southern slopes of the Himalayas, wringing out huge rainfall.

Asian Monsoon Does Have a Weaker North American Version...

However, North America also has a monsoon, although it's not as strong. Sometimes, the winter flow is hard to define, although there can be northwest-to-southeast flow over western North America, as we have when Minnesota is getting cold air masses from Alaska and northwestern Canada. During the summer months, however, high pressure tends to set up somewhere over the southern US or the Gulf of Mexico. The clockwise circulation around the high pushing warm and moist air aloft through the Mexican Plateau from either the tropical Pacific or the western Gulf of Mexico or Caribbean Sea (see article on climate.gov). When that happens, showers and thunderstorms become common across the Mexican Plateau and into the Southwestern US at times. The rainiest season in Arizona is during July and August, which is also its severe weather season. At times, the moisture moves along the ground from the Gulf of California through the Colorado River Valley, pushing dew points into the uncomfortable 60's. With temperatures still about 10 degrees warmer in Arizona than were in Minnesota during our recent heat, it certainly isn't a dry heat during the monsoon season. Elsewhere in the Rockies, the correct south-to-north flow can pull the mid-level moisture throughout the Rockies. It's harder to move the low-level moisture through the mountains, so these thunderstorms can be dry, raising the threat of lightning strikes triggering forest fires.

...It's Going On Right Now...

That Mexican Monsoon dominates the Rockies right now. It has been going on for a while (note the relatively high rainfall totals in Colorado and New Mexico--set date to yesterday and the time period to last 7 days on the NWS Water Prediction Service continental US rainfall map-- where there has been some flooding. The wind pattern at 3-5 miles above the ground shows a dry low on the California coast, and the hot high over Utah and Colorado (clockwise circulation on the College of DuPage North America mid-level water vapor loop), so the air flow is from central Mexico where there are large tropical thunderstorm. The effect of the monsoon flow was scattered afternoon thunderstorms along the mountain tops in much of the Rockies (set number of frames to 200 on the College of DuPage US radar loop). The ground is still very dry from Nevada and Utah northward, since the low-levels are dry (see dew points in the 20's to even teens in Nevada and Utah yesterday on the 4 PM Tuesday NWS WPC North America zoom-in map), so many of these thunderstorms aren't getting rain to the ground. The Weather Channel (and other media hype people) commonly calls the thunderstorms caught up on the edge of the hot high circulation 'ring of fire' thunderstorms.

...And It Will Affect Minnesota Thunderstorms

Why am I monsooning in a St. Cloud, Minnesota weather discussion? When the mid-level south-to-north flow gets far enough to the north, some of the mid-level moisture can add to any low-level humidity to help produce heavy rainfall in Minnesota. The moisture from the heavy Colorado and New Mexico rains during the past week has helped to enhance the major rainfall in Minnesota (3 days in the last week of June with at least 0.99 inch of rain; select St. Cloud area, daily data for a month, and set to June 2025 on the NWS Twin Cities NOWData page).

That mid-level moisture will enhance our rainfall potential once again when the strongest storm system of this week affects our weather, especially Friday and Saturday.

Today, An Early or Late Thunderstorm, Very Warm, and Stickier

Meanwhile, the persistent leftover moisture from the recent rain has pushed dew points back into the uncomfortable 60's in much of Minnesota (see brown areas on the UCAR hourly dew point map). We don't have a strong weather system around, but the beginning of air flow from the Rockies (see College of DuPage North America mid-level water vapor loop), where highs were in the 90's yesterday (see 4 PM Tuesday NWS WPC North America zoom-in map), has produced some thunderstorms in the southern Canadian Prairie Provinces. A few of those showers and thunderstorms have pushed into North Dakota and northern Minnesota (see College of DuPage north central US radar loop) with other early morning storms developing in South Dakota (also see NWS Aviation Weather Center METAR map). So, central Minnesota will have a 1 in 3 chance of a shower or thunderstorm, not only this afternoon, but early this morning as well. There is a small chance of straight-line damaging winds or large hail in this afternoon's storms. (category 1 of 5 as assessed by the NWS Storm Prediction Center) Those leftover clouds may be the only factor keeping highs in central Minnesota, which reached the upper half of the 80's yesterday, from getting to 90 degrees with heat indices in the lower 90's (see NWS Minnesota hourly weather round-up for latest temperatures, dew points, and heat indices).

There is now some smoke from the Canadian wildfires to the north of the border (see daytime hours of the GeoColor satellite loop from Colorado State satellite slider), so our sunshine today may be more hazy.

Improved Chance of Thursday Storms, Especially Afternoon

Still, the most widespread showers and thunderstorms are expected as a strong push of the Rockies heat approaches as a storm in the eastern Pacific moves into Canada (see College of DuPage North America mid-level water vapor loop). The warm front will get into Minnesota sometime tomorrow afternoon or evening, then the cold front will push through sometime on Saturday. Tomorrow, there may be a few scattered (1 in 3 chance) late night and early morning showers and thunderstorms (when hot air tries to move in, the thunderstorms often peak at night) with a better (40%) chance of storms tomorrow afternoon and early evening. Tomorrow's outbreak could be strong in northern Minnesota, especially tomorrow night.

Natural Fireworks Could Interfere With Human Fireworks Friday PM and Night

Then, that cold front will drift into Minnesota Friday night and take most of Saturday to get through the state. I think the best chance for showers and thunderstorms over the next few days will be sometime on Friday night into Saturday morning. Right now, the most likely period for storms would be from late evening Friday night into Saturday morning, but there will be scattered storms during the evening hours. Since the air feeding these storms will be so sultry, there may be a chance for severe weather (straight-line wind damage, large hail) in these thunderstorms, but the more likely issue will be heavy rainfall over areas that have picked up a lot of recent rain. (see Day 4 on the NWS WPC Excessive Rainfall Outlook). I still have a 50-50 chance for the natural fireworks to interfere with the scheduled fireworks for the second time in the past week (central Minnesota festival weekend last weekend). So, those planning any fireworks displays will want to keep alert for Friday evening forecasts. It's probably difficult to reschedule activities, but Saturday evening appears to have a smaller chance of storms (1 in 3) than Friday evening.

Saturday will likely be a cloudy day with chances of showers and thunderstorms all day. I am leaning towards the better chance of storms during the morning as the front slogs through central Minnesota. It could be in southern Minnesota on Saturday afternoon, although the different computer forecasts, which aren't good at predicting thunderstorms, put the Saturday afternoon and evening storms in different places.

Warm and Sticky Today and Tomorrow, Oppressive Friday, Cooler Saturday, With Slightly More Comfortable Humidity by Sunday

Temperature and humidity-wise, we will have highs well up in the 80's with those uncomfortable 60's dew points today. Lows will remain in the 60's tonight. More clouds tomorrow with both the early and late chance for thunderstorms means I will keep the high in the middle 80's, but dew points will climb further into the uncomfortable 60's. If we stay rain-free after the Thursday afternoon and early evening thunderstorm chance, temperatures may stay in the 70's, thanks to a persistent south wind. And, dew points will return to the Florida-like 70's. As long as there aren't any stray morning thunderstorms or leftover clouds, Friday will have the best chance to be similar to last weekend's weather. Highs will be in the lower half of the 90's with dew points in the uncomfortable 70's, so heat indices will be in the 95-102 range.

Friday night will again be warm and sticky, but the likely thunderstorms will knock low temperatures back into the upper 60's. I expect clouds to persist much of Saturday, even between the showers, so I have highs in the upper 70's to near 80.

On Sunday and Monday, the computer forecasts have our winds returning to the northwest, bringing in Canadian air. However, the computer forecasts disagree about what part of the Canadian Prairies or even the Northwest Territories will be the source of our air. Given the wet ground and the good shower and thunderstorm chances in southern Canada over the next 3 days, I am keeping the dew points in the uncomfortable lower 60's and I will at least keep high temperatures in the upper 70's to near 80. And, I still have a 1 in 3 shot at a shower or thunderstorm (note Minnesota has at least a chance for measurable rain during every period Days 1 through 7 on the NWS WPC Quantitative Precipitation Forecast).

The low-level smoke concentrations have produce worse air quality indices during the past day or so in southern Manitoba and central Saskatchewan and have been worse near the fires. However, there will be a good chance for rain in at least southern Canada with the upcoming weather system (see NWS WPC Quantitative Precipitation Forecast), so we'll see if some of the smoke gets washed out.

Beyond Monday, Minnesota will continue to be near the storm track, so there will be more uncertain chances for showers and thunderstorms into the middle of next week. I really don't have a good idea whether we will again get warmer.

June 2025 St. Cloud Weather Summary Available

The June 2025 St. Cloud weather summary has been posted. In it, I discuss the temperature records, both warm and cool, and specifically note how often we get low temperatures of 80 or warmer, like on June 22. Also, I note the various rainfall totals (St. Cloud made it to a top 10 rainiest June) and how often we get a month with nearly 8 inches of rain. I have also linked the storm surveys from all of the Minnesota severe weather outbreaks during the second half of June.

Detailed St. Cloud, MN, and Vicinity Forecast

Confidence Level: "The Bugs Are Waiting for Me to Mow the Lawn"

Wednesday 7/2/2025: Perhaps an early shower or thunderstorm, then mixed clouds and sun, very warm, and uncomfortably humid. A chance of a shower or thunderstorm. High: between 85 and 90. Winds: SW 5-15 MPH. Chance of measurable rainfall: 30%.

Wednesday Night: Partly cloudy, warmer, and uncomfortably humid with a chance of a scattered shower or thunderstorm. Low: between 63 and 68. Winds: SW 5-10 MPH evening, SE 5 MPH late. Chance of measurable rainfall: 30%.

Confidence Level: "Extra Bugs Will Come From Every Home on the Block to Hover Around My Head"

Thursday 7/3/2025: Perhaps an early shower or thunderstorm. Otherwise, a mixture of clouds and some sun and very warm, with uncomfortable to oppressive humidity. A chance for a late day shower or thunderstorm. High: between 83 and 88. Winds: SE 8-18 MPH. Chance of measurable rainfall: 30% in the morning, 40% in the afternoon.

Thursday Night: Perhaps an evening shower or thunderstorm. Otherwise, partly cloudy, breezy, and even warmer with oppressive humidity. Low: between 70 and 75. Winds: S 8-15 MPH. Chance of measurable rainfall: 40% before midnight, 20% during the early morning hours.

Friday 7/4/2025: Mixture of clouds and some sun, hot, and oppressively humid. A chance for a late afternoon shower or thunderstorm. High: between 90 and 95. Winds: SW 10-25 MPH with higher gusts. Chance of measurable rainfall: 40%.

Friday Night: Showers and thunderstorms likely, especially from late evening on. Heavy rainfall likely with severe weather possible. Still uncomfortable to oppressive humidity. Low: between 68 and 74. Winds: SW 10-25 MPH with higher gusts in storms. Chance of measurable rainfall: 50% before midnight, 80% after midnight.

Confidence Level: "Enough Bugs Will Fly into My Mouth to Throw Off My Diet"

Saturday 7/5/2025: A chance of showers and thunderstorms both early in the morning and during the middle and late afternoon. Heavy rainfall is possible. Otherwise, mostly cloudy, not quite as warm, but still uncomfortably to oppressively humid. High: between 75 and 80. Winds: SW 10-20 MPH during the morning, N 10-20 MPH during the afternoon. Chance of measurable rainfall: 60% during the morning, 40% during the afternoon.

Saturday Night: Partly to mostly cloudy with a chance for a scattered shower or thunderstorm. Still uncomfortable humidity. Low: between 63 and 68. Winds: NW 5-10 MPH. Chance of measurable rainfall: 30%.

Sunday 7/6/2025: Lots of clouds with perhaps a few sunny breaks, and continued a bit cooler than average.. A slight chance for a shower or thunderstorm. Slightly less uncomfortable humidity. High: between 75 and 80. Winds: N 5-15 MPH. Chance of measurable rainfall: 30%.

Extended: Continued a bit cooler than average into Monday??? Remaining humid with uncertain thunderstorm chances during the middle of next week???

Forecast Confidence (10 - "The Rabbits Will Thump Even Though I Fed Them"; 0 - "The Rabbits Will Offer To Groom My Bald Spot"): 6 Wednesday and Wednesday night, 5 Thursday, 4 Thursday night through Friday night, 3 Saturday through Sunday.

Yesterday's High: 87°F; Overnight Low (through 2 AM Wednesday): 68°F
St. Cloud Airport 24-Hour Melted Precipitation (through 2 AM Wednesday): None; SCSU 24-Hour Precipitation (through 2 AM Wednesday): None

Next Update: Thursday, July 3, 2025 6 AM

Let me know what you think about this forecast and discussion by emailing SCSU meteorology professor Bob Weisman. Please note that I make the forecast, not the weather!

Are you interested in studying meteorology? If so, go to the Atmospheric and Earth Sciences Department home page.