Heat warnings and advisories in many areas today through Monday

Meteorological summer runs from June through August. It’ll feel truly summery the next couple of days.

Sunday highs will reach well into the 90s across most of Minnesota, and a few spots in west-central Minnesota could top 100 degrees. This will probably be one of the warmest Juneteenths that you’ll ever see.

Northeastern Minnesota and western Wisconsin will see mainly 80s, with some 70s and a few 60s near Lake Superior.

Sunday afternoon dew points will be in the sticky upper 60s in much of Minnesota, with steamy 70s in the southwest.

Heat index values will be around 100 degrees in many parts of Minnesota Sunday afternoon.

Heat index

Here’s a good explanation of heat index, from NOAA:

The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.  This has important considerations for the human body's comfort.  When the body gets too hot, it begins to perspire or sweat to cool itself off.  If the perspiration is not able to evaporate, the body cannot regulate its temperature.  Evaporation is a cooling process.  When perspiration is evaporated off the body, it effectively reduces the body's temperature.  When the atmospheric moisture content (i.e. relative humidity) is high, the rate of evaporation from the body decreases.  In other words, the human body feels warmer in humid conditions. 

Steamy weather continues on Monday

Monday highs will be in the upper 90s in many spots:

A few triple-digit highs are possible Monday afternoon, even in the Twin Cities metro area.

Monday dew points will reach the upper 60s to around 70:

The combination of heat and humidity will create heat index values over 100 in many locations both Sunday and Monday.

Excessive heat warnings and heat advisories begin on Sunday

An excessive heat warning begins at 1 p.m. Sunday in the Twin Cities metro area, and ends at 1 a.m. Tuesday. There is also an excessive heat warning for that same time period in portions of west-central Minnesota, with heat advisories elsewhere in central and much of southern Minnesota:

Here are details of the excessive heat warning:

URGENT - WEATHER MESSAGE National Weather Service Twin Cities/Chanhassen MN 453 AM CDT Sun Jun 19 2022 MNZ047-054>056-060>064-068>070-191800- /O.CON.KMPX.EH.W.0002.220619T1800Z-220621T0600Z/ Stevens-Lac Qui Parle-Swift-Chippewa-Hennepin-Anoka-Ramsey- Washington-Yellow Medicine-Carver-Scott-Dakota- Including the cities of Morris, Madison, Benson, Montevideo, Minneapolis, Blaine, St Paul, Stillwater, Granite Falls, Chanhassen, Chaska, Victoria, Shakopee, and Hastings 453 AM CDT Sun Jun 19 2022 ...EXCESSIVE HEAT WARNING REMAINS IN EFFECT FROM 1 PM THIS AFTERNOON TO 1 AM CDT TUESDAY... * WHAT...Dangerously hot conditions with heat index values up to 100 this afternoon and 106 Monday afternoon, with overnight lows only dropping to around 80. * WHERE...The Twin Cities metro area and west central Minnesota. * WHEN...From 1 PM this afternoon to 1 AM CDT Tuesday. * IMPACTS...Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities. * ADDITIONAL DETAILS...The heat may also result in some roads buckling. PRECAUTIONARY/PREPAREDNESS ACTIONS... Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances. Take extra precautions if you work or spend time outside. When possible reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear lightweight and loose fitting clothing when possible. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency! Call 9 1 1.

You may wonder why the excessive heat warning continues overnight, even though heat index values taper off overnight. That’s because overnight lows in many areas will be in the upper 70s to lower 80s and the sticky dew points will stay with us. Many houses and apartments without air-conditioning will stay hot overnight, making it hard to sleep.

There’s also an excessive heat warning for several counties in northwestern Minnesota on Sunday, with additional northwestern Minnesota counties in a heat advisory (orange):

Here are details of the excessive heat warning in portions of northwestern Minnesota:

URGENT - WEATHER MESSAGE National Weather Service Grand Forks ND 416 AM CDT Sun Jun 19 2022 MNZ001>004-007-030-040-NDZ008-016-027-030-200200- /O.CON.KFGF.EH.W.0001.220619T1500Z-220620T0200Z/ West Polk-Norman-Clay-Kittson-West Marshall-West Otter Tail-Grant- Pembina-Eastern Walsh-Grand Forks-Traill- Including the cities of Crookston, East Grand Forks, Ada, Twin Valley, Halstad, Moorhead, Hallock, Karlstad, Lancaster, Warren, Stephen, Argyle, Fergus Falls, Elbow Lake, Hoffman, Ashby, Herman, Barrett, Cavalier, Walhalla, Drayton, Pembina, Neche, St. Thomas, Grafton, Park River, Grand Forks, Mayville, Hillsboro, Hatton, and Portland 416 AM CDT Sun Jun 19 2022 ...EXCESSIVE HEAT WARNING REMAINS IN EFFECT FROM 10 AM THIS MORNING TO 9 PM CDT THIS EVENING... * WHAT...Dangerously hot conditions with heat index values up to 105 expected. * WHERE...Portions of northwest and west central Minnesota and northeast and southeast North Dakota. * WHEN...From 10 AM this morning to 9 PM CDT this evening. * IMPACTS...Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities. PRECAUTIONARY/PREPAREDNESS ACTIONS... Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances. Take extra precautions if you work or spend time outside. When possible reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear lightweight and loose fitting clothing when possible. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency! Call 9 1 1.

North-central Minnesota and a small part of northeastern Minnesota are in a heat advisory Sunday 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.

Heat safety

Here are some safety reminders to keep in mind during hot, humid weather:

Here are the symptoms of heat exhaustion and heat stroke:

When will it cool off?

Twin Cities metro area highs are projected to reach the lower 90s on Tuesday, followed by mid 80s Wednesday, then lower 90s Thursday and Friday.

Rain chances

Portions of far northern Minnesota could see a passing shower or isolated thunderstorm today. The Twin Cities metro area may have to wait until late Monday for scattered showers and thunderstorms.

Scattered showers and thunderstorms could develop in western Minnesota by mid to late Monday afternoon, then spread to the east-northeast Monday evening and overnight Monday night.

The National Oceanic and Atmospheric Administration’s North American Mesoscale (NAM) forecast model shows the potential rain pattern from 3 p.m. Monday to 6 a.m. Tuesday:

NOAA’s High-Resolution Rapid-Refresh (HRRR) model depicts the most numerous areas of rain shifted a bit to the northwest Monday afternoon through Monday night:

Weather nugget

The last time the official Twin Cities high temp hit 100 degrees (at MSP Airport) was on May 28, 2018. That was on Memorial Day.

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.