Ijams After Dark has been walking people out to Mead's Quarry after sunset all summer to watch bats work the lake, and Thursday is the last date on the calendar. A naturalist teaches you to tell species apart by how they fly, and the park sets up blacklight stations along the way so the insects and everything else drawn to ultraviolet turn up too. It runs eight to nine-thirty, ages ten and up, fifteen dollars.

★The weather is the question

Thursday is the one wet day of the week. The forecast has rain showers likely through the afternoon, a fifty percent chance before eight, and partly cloudy after — which is to say the walk is on the right side of the front, barely. Check the event page before you leave the house, wear shoes for wet rock, and bring a headlamp with a red setting if you own one. The upside is what a front does to the air: Thursday night's low is 59, the first night under 60 since spring.