A steamy Fourth of July; thunderstorm chances highest in the morning

Fourth of July climatology

We have an update on thunderstorm chances this holiday weekend. Here are the highlights:

  • Areas of showers and thunderstorms are possible Sunday evening from southwestern and west-central Minnesota through northeastern Minnesota and northwestern Wisconsin. There could be an isolated shower or thunderstorm elsewhere in Minnesota and western Wisconsin Sunday evening

  • A more organized batch of showers and thunderstorms is expected to spread across much of Minnesota and western Wisconsin in the overnight hours of Sunday night and through Monday morning. Some spots could see heavy rainfall.

  • A few scattered showers and thunderstorms will be possible Monday afternoon and evening.

You can hear updated weather information for Minnesota and western Wisconsin on the Minnesota Public Radio News network, and you can see updated weather info on the MPR News live weather blog.

Severe weather outlook

Here are the severe weather categories that are used in the severe weather outlooks that are issued by the NWS Storm Prediction Center:

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Severe weather risk categories
NWS Storm Prediction Center

The NWS Storm Prediction Center shows a slight risk (shaded yellow) of severe weather Sunday evening and overnight Sunday night in west-central Minnesota and much of South Dakota and North Dakota:

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Severe weather outlook Sunday evening and overnight Sunday night
NWS Storm Prediction Center

Slight risk means that scattered severe thunderstorms are possible. The dark-green shaded area that covers much of Minnesota plus west-central Wisconsin has a marginal risk of severe weather, meaning that an isolated severe thunderstorm is possible.

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The NWS Storm Prediction Center updates the severe weather outlook as needed. They also issue severe weather watches, and they have already issued watches for much of South Dakota this Sunday evening.

The severe weather outlook for 7 a.m. Monday through 7 a.m. Tuesday shows a slight risk (shaded yellow) of severe weather in southeastern Minnesota, southern Wisconsin and eastern Iowa plus northern Illinois:

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Severe weather outlook Monday and Monday night
NWS Storm Prediction Center

SPC shows a marginal risk of severe weather (dark green) for much of Minnesota and central/northern Wisconsin Monday and Monday night. Check forecast updates.

Temperature trends

Fourth of July highs will reach the 80s in most of central and southern Minnesota plus western Wisconsin. A few spots in far southwestern Minnesota could top 90:

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Monday forecast highs
National Weather Service

The northern third of Minnesota will see mainly 70s, with some 60s near Lake Superior.

Dew points will be in the steamy 70s in roughly the southern half of Minnesota Monday afternoon and evening:

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Monday 1 p.m. forecast dew points
National Weather Service

Back to forecast highs, Twin Cities metro area highs are projected to reach the mid 80s on Tuesday, followed by lower 80s Wednesday then mid 80s Thursday and Friday. Our average Twin Cities high temperature is 83 degrees this time of year.

We don’t see any really cool weather in the next week to ten days. The NWS Climate Prediction Center shows a strong signal for above-normal temps in the upper Midwest July 9 through July 13:

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Temperature outlook July 9 through July 13
NWS Climate Prediction Center

We’ll see if that pans out.

Fourth of July climatology

The Minnesota State Climatology Office has posted interesting information about our Fourth of July weather.

Here’s an excerpt from their post:

Looking back at records dating to 1871 for the Twin Cities (1873 for temperature and 1903 for 7 PM dew point temperature), the average high and average low temperatures for Independence Day are 83 degrees F and 64 F, respectively. 2012 came in as the warmest July 4th on record, at 101 degrees, during an extremely warm early July. (link is external)The state record high for the date is 106 F, set in 1988 at Browns Valley. The highest 7 PM dew point for the date in the Twin Cities was 75 F, in 1986.

July 4th can be quite cool too. In 1967 the Twin Cities recorded a high temperature of just 58 degrees, which was the last time the July 4th high temperature failed to reach 70 degrees in the Twin Cities. The record low temperature for the date in the Twin Cities is 43 F, set in 1972. That same year, Tower, MN, recorded a low of 27 F, the state record for the 4th of July.

Their post also shows that it can be stormy:

Several of Minnesota’s most significant straight-line windstorms on record were on or near the 4th of July also, including the infamous Boundary Waters Blowdown of July 4, 1999, when 80-100 mph winds downed tens of millions of trees and stranded hundreds in the Boundary Waters Canoe Area Wilderness. Other convective windstorms with gusts of 100 mph or more stretched from the Lake Minnetonka area to the St. Croix River east of North Branch on July 3, 1983, and across the Brainerd, Mille Lacs, and Pine City areas on July 4th, 1977.

If you are interested, you can check the linked post for Fourth of July highs, lows and rainfall for each year dating back to the 1870s.

Programming note

You can hear my live weather updates on MPR News at 7:35 a.m., 9:35 a.m. and 4:39 p.m. each Saturday and Sunday.