Jupiter's best months are November through April, when temperatures are warm rather than hot, humidity drops, and the afternoon thunderstorms that are a constant feature of Florida summers disappear. Winter daytime temperatures hover around 22–26°C — cool enough for active outdoor pursuits and warm enough to swim. Nights can occasionally be surprisingly cool; a light layer is useful.
Summer (June–September) is hot, very humid, and punctuated by daily downpours, usually in the afternoon. The beaches are less crowded but the heat limits what you can comfortably do outdoors. Sea turtle nesting season runs May through October, with the peak in June and July — nighttime turtle watches on the beach are available. Hurricane season overlaps with summer; Jupiter is not historically prone to direct hits but the threat is real.
The Loxahatchee River is best paddled in winter and spring when water levels are higher and conditions are comfortable. Fishing for snook, tarpon, and redfish is excellent year round.