May to September is the main visitor season. Summer days are long (up to 19 hours of daylight in June), the boat tours run daily, and Exit Glacier is accessible. Temperatures reach 15-20°C on good days. July 4th brings the Mount Marathon Race, which draws large crowds — book accommodation far in advance if you want to be here for it.
October to April: The boat tours mostly stop, Exit Glacier Road closes to vehicles, and snow covers the mountains. The town is quiet and services are limited. However, winter can be beautiful — the mountains are white, the occasional clear day brings spectacular cold-air clarity, and the harbor has a stark, working-port character that summer visitors miss.
The shoulder seasons — May and September — offer fewer crowds with most facilities still operating. September in particular can be excellent: summer temperatures, lower prices, and the salmon running in the streams.
Rain is common throughout summer; bring waterproofs regardless of the forecast. The Kenai Peninsula is notoriously changeable — a sunny morning can become a socked-in fog afternoon within an hour.