In MN schools aren't allowed to hold official practices or tryouts till mid/late March. Partly for academic reasons, partly so multi sport athletes can play their sports. An off season workout program is suggested, though. Season runs from April-late May/early June, depending on how far you go in State. Travel is after that, in the fall....you can go near year round if you want, but very few travel programs run in April and May, and if they do, it's in an extremely limited fashion.
Oh, and if you skip even one HS practice for a travel ball activity you're dog meat.