Hangouts
Hangout reminders and plan heads-ups
Nudge attendees before a hangout, and see weather or venue-hours warnings while you plan.
Reminders you write
When you create or edit a hangout, open Reminders to add timed messages for attendees (what to bring, where to meet, a last-minute detail). Remove any reminder you no longer want sent.
Automatic reminder
Attendees also get a nudge about an hour before the hangout starts. Keep "Hangout reminders" on in Settings → Notifications so those pushes come through.
Weather and venue heads-ups
If a planned place may be closed at your time, or the forecast looks rough (rain, snow, storms, high wind, and similar), you'll see an informational banner on create/edit and hangout detail. These never block you from saving. They're just a chance to double-check or pick a backup.