SOUTHFIELD (CBS/AP) – Michigan’s temperatures have reached Arizona-like levels, with 100-degree-plus readings across a wide area of the state’s Lower Peninsula.

The National Weather Service says that by 5 p.m. Thursday, Ypsilanti’s high temperature had reached 105 degrees. The weather service says the readings in Adrian and Hillsdale have hit 102 degrees, while 100-degree readings are reported at Ann Arbor, Coldwater, Marshall, Mason and Troy.

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CBS 62 Chief Meteorologist Jim Madaus said the heat index will reach even higher and, when you factor in the humidity, it will feel as hot as 105.

The forecast is for more extreme heat for parts of Michigan through Saturday.  A heat advisory is in effect.

An advisory means heat illnesses are possible so people should drink plenty of water and stay out of the sun as much as possible. Madaus says children, seniors and those with conditions such as asthma should limit prolonged outdoor exertion.

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Children and pets should never be left unattended in vehicles under any circumstances. People are advised to check on older relatives and neighbors.  (More on the Heat Advisory here).

In addition, the Southeast Michigan Council of Governments has announced an Ozone Action Day for Thursday, meaning people should not fill up their gas tanks or mow the lawn.

Madaus said that while Thursday will likely be the hottest, the above-average temps will stick around for at least the next seven days — and there’s a chance of thunderstorms through the weekend.

Looking a bit further ahead, Madaus said Metro Detroiters can expect July 4th, Independence Day, to be a toasty one, with a high around 90 degrees and a 40 percent chance of rain.

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For the latest forecast, keep it tuned to WWJ Newsradio 950 for traffic and weather, every 10 minutes on the 8s. To check the local radar anytime or for further forecast details, visit our weather page.