Portsmouth (NH) Temperature by Month
Portsmouth in New Hampshire, United States of America sees significant seasonal temperature differences, with daytime highs between 1°C (34°F) in February and 27°C (81°F) in July, averaging 14°C (57°F) annually. Explore the full monthly breakdown below.
Portsmouth Monthly Temperatures
With significant temperature fluctuations, Portsmouth enjoys distinct seasons year-round. Nighttime lows range from 17°C (63°F) in July to -8°C (18°F) in February.
The chart below illustrates the average maximum day and minimum night temperatures in Portsmouth by month:
The coolest part of the day is typically between 4 AM and 6 AM, while 3 PM is usually the warmest, when solar heating is at its peak. July, the city's warmest month, averages 295 hours of sunshine.
The chart below shows the average temperature throughout the year:
Daily Historical Temperatures
50-year average (1976-2025)
Average high and low temperatures for each day of the month based on long-term records.
Average temperatures in June
Historical Portsmouth Temperatures: 1976-2026
Browse day-by-day temperature records for Portsmouth spanning 51 years. Select any month and year to see actual high and low temperatures recorded on each day.
Temperature: Portsmouth vs the United States of America
The map below shows the annual temperature across the United States of America. You can also select individual months if you want to compare a specific time of year.
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warm
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Portsmouth vs World: Temperature Compared
Portsmouth's average annual maximum temperature is 14°C (57°F). To put that in context, here's how it compares to a few well-known destinations:
Barcelona, Spain has an annual average of around 21°C (70°F), with warm summers and mild, fairly short winters.
Zermatt, Switzerland averages just 4°C (39°F) annually due to its altitude, with very cold winters and cool summers even at its warmest.
Shanghai, China averages 21°C (70°F) a year, with warm summers, mild winters, and a noticeable spring and autumn.
Brisbane, Australia averages 26°C (79°F) a year, with warm winters and hot, humid summers.
What Does the Temperature Feel Like in Portsmouth?
Temperature alone doesn't tell the whole story — humidity plays a big role in how warm or cold it actually feels. High humidity in summer makes the heat feel more intense, particularly once temperatures climb above 25°C. In winter, the same humidity can make cold air feel sharper than the thermometer suggests.
In the cooler months, when temperatures drop below 10°C, high humidity makes the cold feel more cutting than it would in dry conditions.
In Portsmouth, February is the coolest month, with average highs of 2°C (36°F) and humidity around 66% — considered high. In July, the warmest month, temperatures average 27°C (81°F) with 72% humidity — conditions that feel high. For a full picture, see our humidity page.
Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.
The readings come from a range of sources — land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.
Whether a city sits on the coast or deep inland makes a significant difference to its climate. Coastal areas tend to have more stable temperatures year-round — large bodies of water absorb heat slowly in summer and release it gradually in winter, keeping extremes in check. Cities far from the sea don't benefit from that buffer, which is why continental climates tend to have hotter summers and colder winters than their coastal counterparts at the same latitude.
For more on Portsmouth's weather — including monthly rainfall, sunshine hours, and humidity — visit our Portsmouth climate page.
