There's a lot to say about Sunday's weather.
First, temperatures will be hot. Most of the UP will be in the upper 80s to low 90s. The hottest spots will be in the central and western counties. The cooler spots will be near Lake Michigan under a southwest wind where highs may only reach into the upper 70s. Sunday may be one of the hottest days of the year. So far, there have only been two days this year with highs over 90 degrees back in mid July.
Second, it is very humid. Dew points are likely to be in the upper 60s to low 70s. That range of dew points means it is going to be a sticky and uncomfortable day. That level of humidity combined with already hot temperatures will make for heat indices, or apparent temperature, in the mid 90s in the hottest areas.
Please, stay well-hydrated in this heat, and NEVER leave pets or small children in cars in this heat, even for only a few minutes. The National Weather Service has some tips on heat safety.
Finally for Sunday, thunderstorms are likely. All of the heat and moisture around an area of low pressure make perfect conditions for scattered thunderstorms.
Some rain and thundershowers moved past the U.P. overnight and the late morning and afternoon revealed some sunshine, but thunderstorms are still likely to develop in the afternoon, when the day is at its warmest. Some of these storms may be severe.
The greatest potential for severe weather is in the central and western U.P., and in northern Wisconsin, where we could see some high wind and hail. The Storm Prediction Center has issued a Slight Risk for severe weather for part of our viewing area Sunday.
Sunday night, storms are likely to continue. Lows will linger in the upper 60s to around 70, and it will remain very humid. Fog is possible. Scattered thunderstorms will continue until a cold front passes by early Monday.
Monday morning's cold front will likely produce a line of thunderstorms, some of which may be severe. After it passes, much of Monday will be calm and partly cloudy. It will still be hot with highs in the 80s to around 90, but Monday will be the start of a slow cooling trend.
Monday night may see more thunderstorms with the next system to roll through. There is some uncertainty about timing. The same system may arrive on Tuesday. Wither way, it may produce more strong thunderstorms.
By Wednesday, temperatures are likely to approach the seasonal norms in the 70s for this time of year.
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