Free AC ahead, 7th wettest July on record

Minnesota's summer's weather is playing out like a bad B-rated weather disaster movie.

Night of the Nocturnal Bow Echo.

If you've lost a little sleep this month you're not alone. Brainerd Lakes blowdown. Power out for 200,000 in the metro.

Tuesday morning's latest torrential lashing was the 4th significant early morning July storm. I've felt a little like Weather Frankenstein this month stumbling into the Weather Lab in the dark wrestling with the Doppler as lightning and power flashes during every one of our early morning bow echoes. And yes, I've made that guttural groaning noise a few times looking at the maps.

Political Coverage Powered by You

Your gift today creates a more connected Minnesota. MPR News is your trusted resource for election coverage, reporting and breaking news. With your support, MPR News brings accessible, courageous journalism and authentic conversation to everyone - free of paywalls and barriers. Your gift makes a difference.

Sleep deprived weather deja vu July indeed.

The morning commute Tuesday reminded me of winter. In January it only takes a light icy dusting to throw the Twin Cities highways into paralysis. A half hour with rainfall rates of 2 to 3 inches per hour in summer? Instant ponds on many Twin Cities roadways. No severe weather watches or warnings required. That's why the impact of any given weather event doesn't always translate into neat meteorological categories.

728 msp2
Ponding water on I-394 near Dunwoody Blvd. MNDOT

Seventh wettest July on record

Tuesday morning's deluge of 1.29 inches at MSP Airport now makes this the seventh wettest July on record at MSP.

  • 7.32" July rainfall at MSP Airport

  • 7th wettest July on record

728 7th th
Minnesota Climate Working Group

Home Depot is the lucky retailer who benefited from a new sump pump and battery backup system purchase for the Weather Lab today.

Free AC ahead

Our next summer cool front is more noticeable. High pressure pushes a delightful air mass southeast from western Canada behind the departing cold front. An unusually strong low pressure system for late July tracks through Ontario. You'll notice the gusty winds Wednesday, as dew points plunge into the comfortable 50s and stay there for a few days. Our inbound air mass has a hint of late summer in the evenings this week.

728 allfcsts_loop_ndfd (1)
NOAA

This is the weather many Minnesotans celebrate. Sunny warm days. Cooler nights. Less humidity. Good sleeping weather. Best weather on the planet. Does it get any better than this?

728 kky6
Weatherspark

Warmest day of the year behind us now?

The thermometer peaked at 92 degrees at MSP Airport on June 9. That's been the warmest reading at MSP so far this summer.

It's interesting to note that while we've only logged two days of 90 degree heat (30-year average is 11 days) in the metro this summer, overall summer temperatures are almost exactly average. Days with 90 degree heat can be a misleading measure of summer temperatures. When you add up the daily highs and lows since June 1, this is what you get.

  • +0.6 degrees - June monthly average temp at MSP Airport

  • -0.7 degrees - July monthly average temp to date at MSP

On average we've just crossed through the warmest days of the year in Minnesota. The weeks surrounding July 17 produce the highest daily average minimum and maximum temperatures in Minnesota. At MSP Airport , the average daily high peaks at 84 degrees from July 6 through July 22nd.

Here's a look at the average warmest day of the year across the U.S.

US-Warmest-Day-of-the-Year-Map
NOAA

The explanation from NOAA.

Although the amount of solar radiation reaching Earth peaks at the summer solstice on June 21 in the Northern Hemisphere, temperatures for most of the United States tend to keep increasing into July. The temperature increase after the solstice occurs because the rate of heat input from the sun during the day continues to be greater than the cooling at night for several weeks, until temperatures start to descend in late July and early August.

But, this isn’t the case everywhere! The “Warmest Day of the Year” maps show just how variable the climate of the United States can be. For instance, the June values in New Mexico and Arizona reflect the North American Monsoon, a period of increased rainfall affecting the U.S. Southwest. Because these areas tend to be cloudier and wetter from July through September, the temperature is highest on average in June. Similarly, the persistence of the marine layer along the Pacific Coast leads to cool temperatures in early summer with the warmest days on average later in the season.

Is summer's hottest day behind us? Something tells me we'll see more 90s as we approach the Minnesota State Fair in August.

More stagnant summers?

Yes, it's felt a little close out there lately. Climate Central has an interesting piece on how the number of stagnant air days is increasing in the U.S. An extra week of stagnant air in the Twin Cities each year? How lovely.

2015AirStagnation_minneapolis
Climate Central

Climate Central looked at how the number of summer “stagnation days” for cities across the U.S. had changed since 1973 using the National Centers for Environmental Information’s Air Stagnation Index. The ASI uses a combination of upper air wind, surface wind and precipitation data to determine days when conditions are ripe for pollutants to build up in the air.

The analysis found that stagnation days had increased across much of the country, most noticeably in the Southwest and Southeast. For example, in San Francisco there are on average 23 more stagnant air days each summer now than there were 40 years ago, while in New Orleans there are 28. 

Enjoy the fresh breeze and free AC!