The highest day temperature in September 2025 was 88°F. The lowest night temperature was 48°F. The average values for day and night temperatures during September were 77.7°F и 61.8°F respectivly.

The average sea surface temperature in September 2025 for New Haven was 72.8°F. The maximum and minimum values were 71.4°F and 75.4°F respectively.

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

Precipitation total in September for New Haven is 1.2 in.

The average wind speed in September is 8.0 mph. It makes September one of the most windless months of the year for New Haven.

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 New Haven in September is 7.7 hours.