Record-breaking heat possible Tuesday, Wednesday in southern Minnesota
Heat index values could be as high as 110 to 115
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The combination of highs well into the 90s and dew points in the mid to upper 70s will create dangerously hot conditions in the afternoons Tuesday and Wednesday.
Excessive heat warning Tuesday, Wednesday
Excessive heat warnings take effect Tuesday and Wednesday for the potentially hazardous combination of high heat and unusually humid air.
Temperatures will top out in the mid to upper 90s, even potentially 100 for some places in southern Minnesota Tuesday and Wednesday.
The real reading to watch though is the heat index. The extreme dew points mean it is difficult for our bodies to keep cool in the heat. We will see heat index values in the 105 to 115 range.
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In northern Minnesota it will be a very different story, north of the front. Highs in northern Minnesota will mainly be in the 60s and 70s.
Another way to measure heat’s impact: Wet-bulb globe temperature
Heat index is one measurement of what the air really feels like when we combine temperature and dew point, but another measure is the wet-bulb globe temperature.
Both measure the stress of heat on our bodies but the heat index is mainly a measure of temperature and moisture in the shade while wet-bulb globe temperature combines several measurements: temperature, moisture, wind speed, and cloud cover or sun angle.
One can make the argument that wet-bulb globe temperature is actually a better measurement of overall stress on our body, especially if you’re outside in the sun. The wet-bulb globe temperature will be lower than the heat index because they’re different measurements.
The wet-bulb globe temperature measures the temperature that your skin surface can cool to potentially. If the air is drier and you’re in the shade with wind blowing, your skin can cool efficiently.
In hot, humid air with little wind and in the sun, your skin will not cool much and the body temperature can overheat. Readings over 84 degrees are considered dangerous and physical activity should be avoided outdoors.
Cooling off by week’s end, but lacking rainfall
We’ll gradually cool off after Wednesday. Highs will still be near 90 in southern Minnesota Thursday but drop into the mid-80s Friday and by the weekend most of us will be in the 70s statewide.
Unfortunately, there will not be much in the way of rainfall. Northeastern Minnesota has the best chance of some thunderstorms Thursday night into Friday.
