The highest day temperature in September 2026 was 85°F. The lowest night temperature was 49°F. The average values for day and night temperatures during September were 68.6°F и 58.3°F respectivly.

The average sea surface temperature in September 2026 for Lake Geneva was 73.4°F. The maximum and minimum values were 69.6°F and 78.8°F respectively.

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

Precipitation total in September for Lake Geneva is 2.1 in. It makes september one of the least rainy months of the year.

The average wind speed in September is 4.6 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 Lake Geneva in September is 8.4 hours.