Hot Spell is a Nordic-inspired outdoor sauna that began as a weekend pop-up and now runs from Wulff Lodge in Grant Park, South Milwaukee, above the Seven Bridges Trail. It has two wood-fired saunas, cold showers and an open-air rest area among the trees. Shared 75-minute social sessions cost $37, and private sessions for up to 16 people cost $299. Guests must be 18 or older, and sessions run rain or shine.