Climate Insights for Portsmouth

The climate in Portsmouth is temperate. The average annual temperature is 10°C and approximately 1165mm of precipitation falls per year. Portsmouth receives a notable amount of rainfall throughout the year, including during its driest month. Portsmouth 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 -4°C. Snowfall occurs from January to December, with around 148cm accumulating over the season.

Temperatures in Portsmouth vary considerably across the year, with a 29°C difference between the coldest and warmest months. The warmest month is July, when average highs reach 25°C and the mean temperature sits around 22°C. The coldest month is January, when overnight lows fall to -4°C and the daily average is -1°C. Daily temperature variation is modest, with an average difference of 6°C between highs and lows. The sharpest temperature change occurs between October and November, with a 6°C shift in average temperatures.

Portsmouth is a moderately rainy area, receiving approximately 1165mm of precipitation annually, which averages out to around 97mm per month. The wettest month is December, averaging 129mm of rainfall. April and October also tend to see above-average precipitation. The driest month is September, with just 75mm. That's 54mm 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 148cm accumulating over the season. February typically sees the most snow at around 41cm.

Portsmouth is mildly breezy, with an average annual wind speed of 16km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is January, averaging 19km/h, though still comfortable for most outdoor activities. The calmest conditions occur in August, with average winds dropping to 12km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 7km/h gap between the calmest and windiest months. Wind tends to be stronger during winter months, driven by seasonal pressure systems. The seasonal averages break down to 18km/h in winter, 16km/h in spring, 13km/h in summer, 16km/h in autumn.

It is currently summer in Portsmouth, which began on June 21, 2026. Portsmouth 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 25°C, while the coldest stretch bottoms out in January near -4°C. Autumn is next, beginning on September 23, 2026 (7 days from now).

The best time to visit Portsmouth is during June, July, August and September, when the weather is most comfortable for travellers. During these months, average temperatures hover around 20°C with modest rainfall averaging 82mm per month. By contrast, January can be quite cold with temperatures dropping to -4°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 Portsmouth 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.