Portsmouth (NH) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Portsmouth.
Climate overview of Portsmouth
Temperatures in Portsmouth, New Hampshire, United States of America, vary greatly throughout the year. July is the hottest month at 27°C (81°F), while January is the coldest at 1°C (34°F).
The city receives considerable rain/snowfall, with around 1315 mm (52 in) annually. June is the wettest month. It has warm summers and very cold winters. The sunniest month is July, with 9.8 hours of sunshine per day on average.
Portsmouth Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Portsmouth - and find the best time to visit.
Monthly Temperature in Portsmouth
The climate in Portsmouth is known for significant temperature differences throughout the year, making the weather dynamic. Typically, average maximum daytime temperatures range from a comfortable 27°C (81°F) in July to a very cold 1°C (34°F) in the coolest month, January.
Nights vary from 17°C (63°F) in July to around -8°C (18°F) during the colder months.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Portsmouth
Portsmouth has a notably wet climate with abundant precipitation, recording 1315 mm (52 in) of rain/snowfall per year. Precipitation levels in Portsmouth remain relatively steady throughout the year. June has the most rain, with 139 mm (5.5 in) over 14 days. In the driest month January, this drops slightly to 86 mm (3.4 in), making the city's climate fairly predictable. For more details, please visit our Portsmouth Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Sunshine Hours in Portsmouth
For those who appreciate different seasons, Portsmouth serves as an ideal destination. Expect longer, more sun-filled days in July with an average of 9.8 hours of sunshine daily, and embrace the darker days in November, offering only 4.2 hours of daily sunlight.
Visit our detailed sunshine hours page for more information.
Monthly hours of sunshine
Daily hours of sunshine
Humidity in Portsmouth by Month
The relative humidity is high throughout the year in Portsmouth.
The city experiences its highest humidity in September, reaching 76%. In April, the humidity drops to its lowest level at 62%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Best Time to Visit Portsmouth
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
- Best overall: September
- Warmest weather: July and August
- Most sunshine: July
- Fewer rainy days: February, March, August, September and November
- Seasonal pattern: Warm summers and very cold winters
- Coldest conditions: January, with freezing nights around -8°C (18°F).
Frequently asked questions about the climate in Portsmouth
What is the best time to visit Portsmouth?
September typically offers the most optimal weather in Portsmouth. In contrast, January, February, March, April, November and December tend to have less optimal conditions. Portsmouth has warm summers and very cold winters.
What temperatures can I expect in Portsmouth?
Daytime highs range from 1°C (34°F) in January to 27°C (81°F) in July. Nighttime lows range from -8°C (18°F) to 17°C (63°F). Temperatures vary considerably through the year.
How much rain does Portsmouth get?
Annual rainfall is around 1315 mm (52 in). June is the wettest month with 139 mm (5.5 in), while January is the driest with 86 mm (3.4 in).
How sunny is Portsmouth?
Portsmouth receives around 2,512 hours of sunshine per year. July is the sunniest month with 295 hours, while November is the cloudiest with just 127 hours. Overall, Portsmouth enjoys abundant sunshine.
Portsmouth 3-Day Forecast
Portsmouth (NH) 3-Day Forecast
Portsmouth on the map
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