It's a subtle change, but the National Weather Service hopes it'll make Wisconsin residents pay more attention to storm warnings.

The agency typically issues a severe-thunderstorm warning when hailstones are expected to be at least 3/4 inch in diameter. That's about the size of a penny.

But starting next month, hailstones will have to be at least a full inch in diameter to prompt a warning. That's about quarter-sized.

Meteorologist Penny Zabel says the change reflects the fact that hailstones generally don't cause damage unless they're at least an inch in diameter.

She says there aren't statistics on how many warnings were issued last year and how many would have been avoided under the new rule. She says that data will be collected this year.