Climate Insights for Groton

The climate in Groton is temperate. The average annual temperature is 11°C and approximately 1293mm of precipitation falls per year. Groton receives a notable amount of rainfall throughout the year, including during its driest month. Groton is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: July, August, June. The coldest months are January, February, December, when temperatures can drop to -3°C. Snowfall occurs from January to December, with around 124cm accumulating over the season.

Temperatures in Groton vary considerably across the year, with a 31°C difference between the coldest and warmest months. The warmest month is July, when average highs reach 28°C and the mean temperature sits around 24°C. The coldest month is January, when overnight lows fall to -3°C and the daily average is 0°C. Daily temperature variation is modest, with an average difference of 8°C between highs and lows. The sharpest temperature change occurs between October and November, with a 7°C shift in average temperatures.

Groton is a fairly wet location, receiving approximately 1293mm of precipitation annually, which averages out to around 108mm per month. The wettest month is December, averaging 133mm of rainfall. October and April also tend to see above-average precipitation. The driest month is September, with just 88mm. That's 45mm less than December, the wettest month. Rainfall is relatively evenly distributed throughout the year, so there is no pronounced dry or wet season to plan around. Snowfall is a regular feature from January to December, with around 124cm accumulating over the season. March typically sees the most snow at around 39cm.

Groton is relatively calm, with an average annual wind speed of 3km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is March, averaging 4km/h, though still comfortable for most outdoor activities. The calmest conditions occur in July, with average winds dropping to 3km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 1km/h gap between the calmest and windiest months.

It is currently spring in Groton, which began on March 20, 2026. Groton is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in July at around 28°C, while the coldest stretch bottoms out in January near -3°C. Summer is next, beginning on June 21, 2026 — 7 days from now.

The best time to visit Groton is during June and September, when the weather is most comfortable for travellers. During these months, average temperatures hover around 19°C with modest rainfall averaging 92mm per month. By contrast, July can be uncomfortably hot with highs reaching 28°C, while January is the coldest period with lows dropping to -3°C. Despite being the best months overall, some rain is still likely — pack a waterproof layer and plan a mix of indoor and outdoor activities.

The table below shows monthly climate averages for Groton based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.