The highest day temperature in September 2025 was 96°F. The lowest night temperature was 57°F. The average values for day and night temperatures during September were 83.3°F и 67.0°F respectivly.

The average sea surface temperature in September 2025 for Washington was 77.4°F. The maximum and minimum values were 75.2°F and 80.8°F respectively.

Most of the days in September are sunny but you can also expect cloudy and gloomy days.

Precipitation total in September for Washington is 2.2 in.

The average wind speed in September is 6.3 mph. It makes September one of the most windless months of the year for Washington.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Washington in September is 7.5 hours.