March - April & May in Wisconsin are what I would consider "dicey" months to shoot outside. Wisconsin is... Wisconsin. It could be freezing cold one day and 65 degrees the next. The trails and going off road would not be very advisable as the snow is still melting and slipping on mud is very likely.
If Spring is desired - think of jeans, long sleeves, and maybe even a light jacket.
June - July & August in Wisconsin are the hottest months of the year. More ability to go off roading, more accessibilities with trails. It's the perfect time of year to wear dresses, shorts, and floppy sun hats.
September- October & November In Wisconsin is another cluster of months I would consider "dicey." I would say your safest month in Autumn would be September, and the first week in October. This is one of my most favorite times to photograph in Wisconsin. Chunky sweaters, long dresses and cute little jackets are always a plus!
December- January & February in Wisconsin makes most Wisconsinites wonder why we live here. But, it can turn to be some of the prettiest pictures with a nice dusting of snow on the ground. The reflection of light bouncing off snow flakes makes for some pretty beautiful pictures and skin tones. Most of my Winter brides have beautiful fur coats and pockets to warm their hands.