Swimsuit. Sunscreen. Skis. You’re ready: Celebrate your independence by schussing the slopes during the longest snow season in California history. While the rest of America has moved on to lawn parties and backyard barbecues, happy skiers are still carving turns through the sweet, sticky pockets of lingering snow in the Sierra Nevada — where weekend lifts are spinning for the ninth straight month, even as temperatures soar to the mid-70s. But California’s snowiest winter on record means major delays — or danger — for equally beloved summer sports such as backpacking, hiking, trail running, kayaking and rafting.