Whether Seattle records a routine summer high or an extreme heat day matters for public health, electric demand, and outdoor-event planning.

The recorded maximum temperature at Seattle–Tacoma Airport on July 22, 2026 decides which discrete outcome bucket resolves, from typical highs through the 100°F-or-above threshold.

The National Weather Service Seattle forecast office, Sea‑Tac and Boeing Field observation stations, and private forecasters and TV meteorologists provide official and public temperature readings.

NOAA model teams, university research groups, and airport instrumentation staff maintain the observations and model output that determine the reported daily maximum.

Pacific high pressure strength, the presence or absence of an inland heat dome, and the timing/intensity of the marine layer primarily determine daytime warming across the Puget Sound region.

Short-term shifts in model guidance (GFS, ECMWF), onshore wind timing, cloud cover, and humidity will push the forecast between low‑90s and triple‑digit extremes.

48–72 hour model runs and daily NWS forecast updates in the days immediately before July 22 will show the clearest signal for extreme heat.

Monitor Sea‑Tac hourly observations, morning sounding profiles, visible satellite imagery, and any NWS heat watches or advisories released 1–3 days ahead.