Portsmouth

Planning a trip or just curious about the weather in Portsmouth? Here you'll find the most up-to-date weather information, including detailed forecasts and helpful charts.

The climate in Portsmouth, USA, can be described as temperate with four distinct seasons. The city experiences cool winters, warm and pleasant springs, hot summers, and mild, comfortable autumns. This means visitors can expect significant changes in weather depending on the time of year, allowing for trips planned around different activities and preferences.

Summer months, from June to August, are the warmest, with average temperatures ranging from 23.6°C to 26.7°C, with July being the hottest month of the year. Winters, from December to February, are quite cool, with average temperatures between 5.1°C and 7.5°C. Spring and autumn offer mild and pleasant conditions for travel. Precipitation in Portsmouth is relatively low throughout the year, ranging from 2 to 5 mm per month. While there is no distinct rainy season, July and August stand out with the highest number of rainy days (16 and 15 days, respectively), which can create a feeling of increased humidity at the height of summer.

The city of Portsmouth, USA, experiences a noticeable shift in temperature regimes throughout the year, offering diverse climatic conditions for visitors. The hottest month is usually July, when average temperatures reach 26.7°C. During this period, daytime highs can rise to 30.6°C, creating a true summer atmosphere. Conversely, January is considered the coldest month, with an average temperature around 5.1°C, and average nightly lows dropping to 1.0°C, bringing a chill.

The summer season in Portsmouth, spanning from June to August, is characterized by warm and occasionally hot weather. In June, the average temperature settles at 23.6°C, gradually climbing toward the July peak. Even summer nights remain warm: for instance, in July, the minimum average temperature is a comfortable 22.8°C. In August, the heat eases slightly, but the average temperature still holds at a high 25.5°C, providing a long period of warm weather.

Winter in Portsmouth is notable for its mildness. In December, the average temperature is 7.2°C, while in February, it’s slightly higher at 7.5°C. January, despite being the coolest, doesn't bring severe frosts: average daytime highs stay around 9.2°C, and while nightly temperatures drop, they generally remain above freezing on average. Temperature fluctuations between day and night occur year-round, averaging 8–9°C, which is typical for the region and doesn't cause sharp changes.

Portsmouth sees relatively stable precipitation throughout the year, without a distinct rainy or dry season. However, some months have slightly higher or lower rainfall volumes. Overall, the city's precipitation level is characterized as low, with the total annual amount distributed fairly evenly.

The highest precipitation occurs during the summer months. July and August stand out as the wettest, with an average of 5 mm each. These months also record the maximum number of rainy days: about 16 days in July and 15 days in August. A small increase in precipitation is also seen in June (4 mm and 11 wet days). The "driest" month by volume is November, with only 2 mm falling. November, along with October, also features the fewest rainy days—averaging 8 days each.

Given the small total volume of precipitation even in the "wettest" months, it suggests that Portsmouth typically experiences light precipitation. In the warmer months, this is likely rain or drizzle rather than heavy downpours. During the cold months, such as January (average low of 1.0°C), February (3.1°C), and December (3.3°C), some of this precipitation could theoretically fall as snow, though the data provided doesn't specify the type. The frequency of precipitation varies from 8 days in October and November to 16 days in July, indicating regular but mostly minor rainfall throughout the year.

When planning a trip to Portsmouth, it’s important to account for the changeable weather throughout the year and be prepared for various conditions. Dressing in layers is key, as temperatures can shift noticeably even within a single day. Regardless of the season, be sure to bring comfortable walking shoes, as the city is best explored on foot. Given that the number of rainy days remains relatively high all year round (8 to 16 days per month), a light waterproof jacket or a compact umbrella will be reliable companions, even if total precipitation is low.

During the winter months (December to February), when average temperatures range from 5°C to 7.5°C and minimums can drop to 1°C, you’ll need warm clothing. Pack sweaters, a warm jacket, a hat, gloves, and a scarf. Waterproof shoes will also come in handy. In spring (March–May) and autumn (October–November), the weather is transitional: days can be either cool or pleasantly warm. It’s recommended to bring clothes that are easy to layer: T-shirts, long-sleeves, a fleece, and a windbreaker or mid-season jacket.

Summer in Portsmouth (June to August) is warm and even hot, with average temperatures from 23°C to 27°C and maximums reaching 30°C. Light and breathable items like T-shirts, shorts, dresses, and sandals are perfect for this time. Don't forget sunscreen, a hat, and sunglasses for sun protection. Despite the summer heat, July and August have the highest number of rainy days, so a light raincoat or umbrella might still be useful for sudden, though usually light, showers.