Historical weather data, all-time temperature records, and monthly climate averages for Issaquah, WA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in Issaquah runs cool and damp — expect a high around 56° with a 62% chance of rain. The date has seen some wild swings over 117 years of records, from a balmy 76° in 1952 down to a sharp 25° overnight low in 1936.
Issaquah's weather has real range. The all-time high of 112° on June 28, 2021 was a brutal outlier during the Pacific Northwest heat dome, while the coldest ever recorded was exactly 0° in February 1989. On the wet side, a single October day in 2003 dumped 5.5 inches of rain.
Summer is the clear winner for comfortable weather, with late July averaging highs of 78° and staying dry. The first week of January is the coldest stretch, hovering around 43°, while mid-to-late November is the soggiest — expect over 2 inches of rain in a single week. Spring and fall are mild but wet, so pack a layer either way.