The last day Knoxville's airport recorded a high in the 70s was June 23. Since then, every single day has topped 80, most of them 90 or better, and the last three weeks have run 86 to 98. That ends Thursday, when a front comes through with rain, and what follows is the weekend South Knoxville has been waiting on since spring: Friday 77 and mostly sunny, Saturday 77 and sunny, Sunday 78, with nights in the low 50s.

★What that does to the trails

The Urban Wilderness is more than a thousand forested acres along the south bank with over sixty miles of trail and greenway, anchored by Ijams Park, Baker Creek Preserve, the River Bluff Natural Area and the Forks of the River. For three months the only usable hours have been the first two after sunrise. This weekend the whole day is usable — a nine o'clock start at Baker Creek in the low 60s, or a four o'clock loop with the sun still up until 7:26.

Two notes for the first cool weekend. The trails will be busy, especially the Baker Creek flow trails and the Mead's Quarry loops, and the Saturday noon kickoff empties them for three hours in the middle of the day if you want them to yourself. And Thursday's rain means Friday morning is the muddy window; by Saturday the surface will have set up. Every trailhead in the district is free.