Monthly weather forecast and climate
Portsmouth, NH

Bright neon lights and buildings next to the very calm waters of the iconic Piscataqua River in Portsmouth, New Hampshire
Bright neon lights and buildings next to the very calm waters of the iconic Piscataqua River in Portsmouth, New Hampshire

Weather in January

January, the same as December, in Portsmouth, New Hampshire, is another subzero cold winter month, with average temperature fluctuating between 21.2°F (-6°C) and 31.8°F (-0.1°C). January is the coldest month, with an average high-temperature of 31.8°F (-0.1°C) and an average low-temperature of 21.2°F (-6°C). Weather in January »

Weather in February

February, the last month of the winter, in Portsmouth, is a cold month, with average temperature fluctuating between 34.2°F (1.2°C) and 22.3°F (-5.4°C). In Portsmouth, the average high-temperature in February is almost the same as in January - a wintry 34.2°F (1.2°C). Weather in February »

Weather in March

The first month of the spring, March, is still a cold month in Portsmouth, New Hampshire, with temperature in the range of an average low of 28.8°F (-1.8°C) and an average high of 40.5°F (4.7°C). In March, the average high-temperature slightly increases, from a wintry 34.2°F (1.2°C) in February, to a still cold 40.5°F (4.7°C). Weather in March »

Weather in April

April in Portsmouth, New Hampshire, is a fresh spring month, with average temperature varying between 38.8°F (3.8°C) and 51.1°F (10.6°C). In Portsmouth, the average high-temperature in April rises, from a cold 40.5°F (4.7°C) in March, to a fresh 51.1°F (10.6°C). Weather in April »

Weather in May

May, the last month of the spring, in Portsmouth, is an enjoyable month, with average temperature ranging between max 61°F (16.1°C) and min 48°F (8.9°C). In May, the average high-temperature increases, from a cool 51.1°F (10.6°C) in April, to an enjoyable 61°F (16.1°C). Weather in May »

Weather in June

June, the first month of the summer, in Portsmouth, is an agreeable month, with average temperature fluctuating between 69.3°F (20.7°C) and 55.4°F (13°C). In June, the average high-temperature marginally rises, from an enjoyable 61°F (16.1°C) in May, to a pleasant 69.3°F (20.7°C). Weather in June »

Weather in July

July is a moderately hot summer month in Portsmouth, New Hampshire, with average temperature fluctuating between 62.6°F (17°C) and 76.3°F (24.6°C). The warmest month is July, with an average high-temperature of 76.3°F (24.6°C) and an average low-temperature of 62.6°F (17°C). Weather in July »

Weather in August

August, the last month of the summer, in Portsmouth, is another warm month, with average temperature fluctuating between 61.7°F (16.5°C) and 75.7°F (24.3°C). In August, the average high-temperature is essentially the same as in July - a still warm 75.7°F (24.3°C). Weather in August »

Weather in September

The first month of the autumn, September, is also an agreeable month in Portsmouth, New Hampshire, with temperature in the range of an average low of 56.1°F (13.4°C) and an average high of 69.1°F (20.6°C). In September, the average high-temperature slightly decreases, from a warm 75.7°F (24.3°C) in August, to an agreeable 69.1°F (20.6°C). Weather in September »

Weather in October

October, like September, is a moderate autumn month in Portsmouth, New Hampshire, with average temperature fluctuating between 47.1°F (8.4°C) and 57.9°F (14.4°C). In October, the average high-temperature drops, from a pleasant 69.1°F (20.6°C) in September, to a mild 57.9°F (14.4°C). Weather in October »

Weather in November

November, the last month of the autumn, in Portsmouth, is another chilly month, with temperature in the range of an average high of 47.1°F (8.4°C) and an average low of 36.1°F (2.3°C). In Portsmouth, the average high-temperature in November drops, from a moderate 57.9°F (14.4°C) in October, to a frosty 47.1°F (8.4°C). Weather in November »

Weather in December

The first month of the winter, December, is still a cold month in Portsmouth, New Hampshire, with average temperature fluctuating between 28°F (-2.2°C) and 37.6°F (3.1°C). In Portsmouth, the average high-temperature decreases, from a chilly 47.1°F (8.4°C) in November, to a wintry 37.6°F (3.1°C). Weather in December »
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FAQ

What is the coldest month in Portsmouth?

January is the coldest month in Portsmouth, with an average high-temperature of 31.8°F (-0.1°C) and an average low-temperature of 21.2°F (-6°C).

How many days does it rain in Portsmouth?

In Portsmouth, during the entire year, the rain falls for 144.2 days and collects up to 27.48" (698mm) of precipitation.

When does it snow in Portsmouth?

January through April, October through December are months with snowfall in Portsmouth, New Hampshire.

How many days does it snow in Portsmouth?

In Portsmouth, during the entire year, snow falls for 35.2 days, and aggregates up to 16.97" (431mm) of snow.

What is the snowiest month in Portsmouth?

The month with the most snowfall is January when snow falls for 8.8 days and typically aggregates up to 4.02" (102mm) of snow.

When is the lowest UV index in Portsmouth?

January through March, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Portsmouth, New Hampshire.

What is the month with the least sunshine in Portsmouth?

February and December, with an average of 4.8h of sunshine, are months with the least sunshine.

When is the ocean coldest in Portsmouth?

The month with the coldest seawater in Portsmouth is March, with an average ocean temperature of 38.5°F (3.6°C).

What are the least humid months in Portsmouth?

April and November, with an average relative humidity of 75%, are the least humid months.

When it does not snow in Portsmouth?

May through September are months without snowfall in Portsmouth, New Hampshire.

What is the most humid month in Portsmouth?

June is the most humid month, with an average relative humidity of 80%.

When are the longest days in Portsmouth?

The month with the longest days in Portsmouth, New Hampshire, is June, with an average of 15.3h of daylight.

What is the warmest month in Portsmouth?

With an average high-temperature of 76.3°F (24.6°C) and an average low-temperature of 62.6°F (17°C), July is the warmest month in Portsmouth, New Hampshire.

When is the highest UV index in Portsmouth?

Months with the highest UV index in Portsmouth are July and August, with an average maximum UV index of 6.

What month is the ocean warmest in Portsmouth?

With an average ocean temperature of 65.7°F (18.7°C), August is the month with the warmest seawater in Portsmouth.

What month has the most sunshine in Portsmouth?

The month with the most sunshine is August, with an average of 10.6h of sunshine.

What is the driest month in Portsmouth?

September is the month with the least rainfall. Rain falls for 11.3 days and accumulates 1.54" (39mm) of precipitation.

What is the rainiest month in Portsmouth?

The month with the most rainfall is October when the rain falls for 13.3 days and typically aggregates up to 2.83" (72mm) of precipitation.

What is the month with the shortest days in Portsmouth?

The month with the shortest days in Portsmouth, New Hampshire, is December, with an average of 9.1h of daylight.

Average temperature
Portsmouth, NH

Average temperature - Portsmouth, NH

The warmest month (with the highest average high temperature) is July (76.3°F).
The month with the lowest average high temperature is January (31.8°F).

The month with the highest average low temperature is July (62.6°F).
The coldest month (with the lowest average low temperature) is January (21.2°F).

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Average pressure
Portsmouth, NH

Average pressure - Portsmouth, NH

The month with the highest atmospheric pressure is November (30.06").
The month with the lowest atmospheric pressure is June (29.92").

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Average wind speed
Portsmouth, NH

Average wind speed - Portsmouth, NH

The windiest month (with the highest average wind speed) is January (11.7mph).
The calmest month (with the lowest average wind speed) is July (6.6mph).

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Average humidity
Portsmouth, NH

Average humidity - Portsmouth, NH

The month with the highest relative humidity is June (80%).
Months with the lowest relative humidity are April and November (75%).

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Average rainfall
Portsmouth, NH

Average rainfall - Portsmouth, NH

The wettest month (with the highest rainfall) is October (2.83").
The driest month (with the least rainfall) is September (1.54").

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Average rainfall days
Portsmouth, NH

Average rainfall days - Portsmouth, NH

The month with the highest number of rainy days is June (15 days).
The month with the least rainy days is January (7.5 days).

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Average snowfall
Portsmouth, NH

Average snowfall - Portsmouth, NH

The month with the highest snowfall is January (4.02").
Months with the least snowfall are May, June, July, August and September (0").

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Average snowfall days
Portsmouth, NH

Average snowfall days - Portsmouth, NH

The month with the highest number of snowfall days is January (8.8 days).
Months with the least snowfall days are May, June, July, August and September (0 days).

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Average sea temperature
Portsmouth, NH

Average sea temperature - Portsmouth, NH

The best month for swimming (with the highest average sea temperature) is August (65.6°F).
The coldest month (with the lowest average sea temperature) is March (38.5°F).

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Average daylight / Average sunshine
Portsmouth, NH

Average daylight / Average sunshine - Portsmouth, NH

The month with the longest days is June (Average daylight: 15.3h).
The month with the shortest days is December (Average daylight: 9.1h).

The month with the most sunshine is August (Average sunshine: 10.6h).
Months with the least sunshine are February and December (Average sunshine: 4.8).

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Average sunshine days
Portsmouth, NH

Average sunshine days - Portsmouth, NH

The month with the most sunshine days is September (16.8 days).
The month with the least sunshine days is April (13.2 days).

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Average UV index
Portsmouth, NH

Average UV index - Portsmouth, NH

Months with the highest UV index are July and August (UV index 6).
Months with the lowest UV index are January, February, March, November and December (UV index 2).

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Average visibility
Portsmouth, NH

Average visibility - Portsmouth, NH

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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