Lazy, hazy, crazy. Day 12 of 90 degree heat?

Nat King Cole had it right.

If you like it hot and humid, today is your day. This could be day number 12 of 90 degree heat at Minneapolis-St. Paul International Airport this year. Throw in a dew point in the lower 70s, and it feels like 95 across southern Minnesota later this afternoon.

How lovely.

Free sauna

We often call air masses "tropical" when the dew point reaches 70 degrees. The air we're swimming though over southern Minnesota today was soaking up moisture from the Gulf of Mexico a few days ago. Northern Minnesota enjoys a more civilized air mass today.

m(T)

Air masses are named after the source region in which they developed.

Here's more from the National Oceanic and Atmospheric Administration on why we're enjoying a 'Maritime tropical' (mT) air mass across southern Minnesota today.

An air mass is a large body of air with generally uniform temperature and humidity. The area over which an air mass originates is what provides it's characteristics. The longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below. As such, air masses are associated with high pressure systems.

There are two broad overarching divisions of air masses based upon the moisture content. Continental air masses, designated by the lowercase letter 'c', originate over continents are therefore dry air masses. Maritime air masses, designated by the letter 'm', originate over the oceans and are therefore moist air masses.

Each of the two divisions are then divided based upon the temperature content of the surface over which they originate.

• Arctic air masses, designated by the letter 'A', are very cold as they originate over the Arctic or Antarctic regions.

• Polar air masses, designated by the letter 'P', are not as cold as Arctic air masses as they originate over the higher latitudes of both land and sea.

• Tropical air masses, designated by the letter 'T', are warm/hot as they originate over the lower latitudes of both land and sea.

Next low Thursday

The next low pressure wave rides east Thursday across Minnesota. Friday's cool front brings relief from heat and humidity in the form of a fresh northwest breeze.

Stormy Red River Valley

The timing for storms favors northwest Minnesota and the Red River Valley later this evening. A fading wave of storms may approach the Twin Cities early Thursday morning. The question is, will it have enough oomph to survive the trip southeast overnight.

NOAA's North American Mesoscale Forecast System 4 km model grasps the trends of a fading storm wave arriving in the metro just in time for Thursday morning rush hour.

Red River risk

The highest risk for severe storms today and this evening centers on the eastern North Dakota and the Red River Valley.

Weekend weather winning streak?

Another Canadian high pressure cell brings sunshine, cooler temps and comfortable dew points in the 50s this weekend.

Heat spike next week?

The longer range forecast favors a return to heat and humidity next week. NOAA's upper air map shows Minnesota riding the edge of the persistent summer heat dome to the south again next week.

After a lovely weekend, the meteogram suggests two or three more 90-plus degree days next week in the Twin Cities.

Lake Superior warming

Water temperatures near 70 degrees are showing up near Duluth and in Wisconsin's Apostle Islands this week. Temperatures in the mid 60s run along the north shore all the way to Grand Marais. Minn. Lake Superior water temps generally peak in late August or early September.

Swimming anyone?