In September, Sammamish typically sees daytime highs of 20.6°C and overnight lows around 10.3°C. Compared to the annual average high of 15.1°C, September runs +5.6°C.
September in Sammamish averages a daytime high of 20.6°C and an overnight low of 10.3°C.
September runs +5.6°C compared to Sammamish's annual average high of 15.1°C, ranking #3 of 12 months by warmth.
Plan for daytime highs near 20.6°C and cooler evenings around 10.3°C.