The highest day temperature in September 2025 was 89°F. The lowest night temperature was 49°F. The average values for day and night temperatures during September were 69.4°F и 57.8°F respectivly.

The average sea surface temperature in September 2025 for Whidbey Island was 59.4°F. The maximum and minimum values were 56.0°F and 62.6°F respectively.

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

Precipitation total in September for Whidbey Island is 0.7 in. It makes september one of the least rainy months of the year.

The average wind speed in September is 5.2 mph. This value is relatively stable throughout the year.

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 Whidbey Island in September is 7.8 hours.