Winter is a real bona fide season at Mount San Jacinto State Park. Some winters are better than others, with wet years producing several feet of snow in the high country, while dry years producing a dusting or two. If hiking/snowshoeing/skiing into the State Wilderness, you must fill out a wilderness day-use permit. Depending on which side of the park you visit during the winter, call either the Idyllwild Ranger Station (5,600 feet) or the Long Valley Ranger Station (8,400 feet) to inquire about snow conditions.
Note: Mount San Jacinto State Park does not groom snowbound trails. There are no stakes or tree blazes that mark the trails, so you must traverse them at your own risk. Be prepared to navigate with map, compass, and GPS. In addition to your "Hiker's Ten Essentials", you may need to bring specialized snow equipment like microspikes/crampons, trekking poles with snow baskets, snowshoes, ice axes, etc.
Snow play (sledding, snow tubing)