It's still summer, for two weeks and two days more, but cool weather and even a bit of frost hit South Dakota this week, coming on the heels of a hot, windy Labor Day weekend.

"It came quite suddenly, that's for sure," Susan Sanders, meteorologist at the National Weather Service in Rapid City, said.

She said next week, it will warm up to the 70s and maybe even the 80s, "which is closer to normal," she said.

The lower temperatures came just in time to put that back-to-school feeling in the air in Rapid City, where public schools started Tuesday.

Children at Wilson Elementary School seem in the mindset to learn.

"We're liking this," Principal Kathy Conlon said. "We've just had a very smooth start to the school year. The kids seem to be so settled, and I think it's partly due to the weather."

Normally, it's a bit warmer for the first week of school, and teachers at the old school, especially on upper-floor rooms with a southern exposure, rely on fans to keep the air moving, "but not this year," Conlon said.

Temperatures have dipped below freezing in the higher altitudes, and gardeners even in the city worried when they saw frost on their still-ripening tomato plants, but Bill Keck, horticulture Extension agent in Pennington County, said it isn't a big concern. There's only a 10 percent chance of a killing frost before Sept. 10, and a 50 percent chance before the beginning of October.

He said that now is a good time to get out in the yard and fertilize your lawn, and then again toward the end of October, after the frost. "What you do to your lawn now, this fall, will dictate its performance next spring," Keck said.

It is also a good time to get on those home-improvement projects neglected in hotter months. Homeowners throughout town took advantage of the weather to paint and build decks and sheds, according to Dennis Meyers, retail operations manager at Knecht Home Center.

Cooler weather "reminds them that winter's coming - and those honey-dos and those projects they were supposed to get done, they'd better get done," Meyers said.

If you'd rather not spend the last nice days of the year working, it is also a good time to go camping and see tourist sites without the throngs of summer tourists. Craig Pugsley, visitor services coordinator, said Custer State Park campgrounds have been busy but still have plenty of open campsites.

The Associated Press contributed to this report.