4Warn Weather – A 4Warn Weather Alert is in effect as dangerous heat returns to Southeast Michigan, with what is expected to become the region’s second heat wave of July. A heat advisory will be in effect for Tuesday afternoon and evening.
Temperatures reached 90 degrees Monday afternoon at Detroit Metro Airport (DTW), marking the first day of what is forecast to be at least three consecutive days of 90-degree or hotter weather. That meets the meteorological definition of a heat wave in Southeast Michigan.
The first heat wave of the month occurred June 30 through July 3, when heat index values climbed to nearly 110 degrees in some communities under an Extreme Heat Warning. While this week’s event is not expected to reach that level of intensity, it will still bring several days of dangerous heat and little overnight relief.
Warm Monday Night
Skies will remain mostly clear with southwest winds around 5 to 10 mph. Overnight temperatures will only fall into the middle 70s, leaving homes, roads, and buildings with little opportunity to cool. Those warm nights can increase the risk of heat-related illness because the body has less time to recover before the next hot afternoon.
Tuesday: Peak of the Heat
Tuesday is expected to be the hottest day of the stretch.
Afternoon highs will climb to around 98 degrees, while humidity pushes heat index values between 100 and 104 degrees.
Because of the combination of hot temperatures and humidity, the National Weather Service has issued a Heat Advisory for all of Southeast Michigan from noon until 8 p.m. Tuesday.
Temperatures will rise quickly through the morning:
- 6 AM: 72°
- 8 AM: 74°
- 10 AM: 84°
- Noon: 90°
- 2 PM: 95°
- 4 PM: 97°
- 6 PM: 97°
Even after sunset, it will remain uncomfortably warm.
Heat Advisory vs. Extreme Heat Warning
Some people may wonder what separates the two heat alerts.
A Heat Advisory is generally issued when:
- Heat index values are expected to reach 100 degrees or higher for at least three hours, and/or
- Other factors such as consecutive hot days and very warm overnight temperatures increase the risk of heat-related illness.
An Extreme Heat Warning is generally reserved for:
- Heat index values of 105 degrees or higher for at least three hours, and/or
- Dangerous overnight conditions, including lows around 75 degrees or warmer, that prevent adequate overnight cooling and significantly increase cumulative heat stress.
Although this week’s forecast falls just shy of the extreme heat warning warning criteria, it is still dangerous enough to warrant a Heat Advisory, and precautions should be taken.
Wednesday and Thursday
The heat continues.
Wednesday remains very hot with highs in the middle to upper 90s, while Thursday stays hot with highs in the lower 90s. A stray shower cannot be ruled out north Thursday, but most communities remain dry.
Rain chances return late week
The upper-level ridge begins to weaken by Friday, allowing a better chance for showers and thunderstorms. The arrival of clouds and rain should help ease the heat heading into the weekend.
Heat Safety
Heat is one of the nation’s deadliest weather hazards. Take precautions if you’ll be spending time outdoors.
- Drink plenty of water before you become thirsty.
- Wear lightweight, loose-fitting clothing.
- Take frequent breaks in air conditioning or shade.
- Avoid strenuous activity during the hottest part of the day.
- Never leave children or pets in a parked vehicle.
- Check on older adults, neighbors, and anyone without air conditioning.
- Know the warning signs of heat exhaustion and heat stroke. If someone becomes confused, loses consciousness, or stops sweating despite the heat, call 911 immediately.
The 4Warn Weather Team will continue monitoring this developing heat wave and provide updates as conditions change.
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