Check what actually matters
Wait until the rain has stopped, the next shower risk is lower, the cooking area is not slippery, and you can keep food and serving plates dry. A covered gas BBQ may be ready sooner than uncovered charcoal.
Furniture and guests count too
A dry grill is only half the BBQ. Wet chairs, puddled paths, and dripping branches can turn a technically possible BBQ into a deeply indoor evening.
If the grill is ready but the seating is a marsh, call it a cooking experiment, not a party.