The highest day temperature in September 2025 was 75°F. The lowest night temperature was 40°F. The average values for day and night temperatures during September were 61.2°F и 54.2°F respectivly.

The average sea surface temperature in September 2025 for Grand Marais was 59.5°F. The maximum and minimum values were 55.6°F and 64.2°F respectively.

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

Precipitation total in September for Grand Marais is 0.6 in. It makes september one of the least rainy months of the year.

The average wind speed in September is 7.3 mph. It makes September one of the most windless months of the year for Grand Marais.

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 Grand Marais in September is 7.6 hours.