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As the Marx brothers said "There is no sanity clause."

Anywhere that you get rain, get tires with siping. The purpose is to get water out of the tread's contact patch to improve your traction. This is an all year issue. Even a little rain on a surface at the beginning of a wet event can cause slick spots. These encourage skids. It's cheaper to go through tires a little faster so you can avoid damage a lot longer.