Slowly, the leaves in Minnesota’s deciduous canopy are turning color, and autumn officially begins a week from Saturday.

But first, a fresh blast of summer.

A heat advisory is in effect for the Twin Cities metro area and many surrounding counties until 6 p.m. Saturday, according to the National Weather Service in Chanhassen. “Very warm and humid conditions will cause heat indices to rise into the low to upper 90s across the south-central belt of Minnesota,” the Weather Service said. It cautioned people to stay hydrated and avoid overexertion.

That was good advice for the Gophers fans in shorts and sandals at Saturday’s 2:30 game against Miami (Ohio) at TCF Bank Stadium in Minneapolis.

The warm, rain-free forecast was welcome news for thousands of hikers, bicyclists and campers across the state. It was also good news for up to 30,000 motorcyclists participating in Saturday’s annual Fall Flood Run along the Mississippi and St. Croix rivers, traveling between the Twin Cities and Winona. The ride is a fundraiser for Gillette Children’s Specialty Healthcare.

Saturday’s high in the Twin Cities is expected to be around 92, with heat index values up to 98, according to the Weather Service. Saturday night will be mostly clear, with a low around 72.

Sunday will be sunny, with a high near 89 and a low Sunday night around 70, the Weather Service said.

Monday will continue to be hot, with a high near 84. Showers and thunderstorms may develop later Monday.

By Tuesday, the weather will feel more fall-like, with a high near 73 and a low Tuesday night of 56.