Portsmouth
New Hampshire, USA
Long-term weather forecast
Long-term weather forecast

August 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, the clear dusk sky in close up view
Bright neon lights and buildings next to the very calm waters of the iconic Piscataqua River in Portsmouth, New Hampshire, the clear dusk sky in close up view
August, the last month of the summer, in Portsmouth, is another warm month, with average temperature ranging between min 59°F (15°C) and max 77°F (25°C).

Temperature

In Portsmouth, the average high-temperature in August is essentially the same as in July - a still warm 77°F (25°C). The average low-temperature, in August, is 59°F (15°C).

Rainfall

The month with the least rainfall is August when the rain falls for 10 days and typically collects 2.8" (70mm) of precipitation.

Ocean temperature

August is the month with the warmest seawater in Portsmouth, with an average ocean temperature of 65.7°F (18.7°C).
Note: For most, swimming in 65.7°F (18.7°C) is not an enjoyable activity. Furthermore, controlling your breathing becomes progressively more difficult as the water temperature decreases from 69.8°F (21°C) to 59°F (15°C).

Daylight

In August, the average length of the day in Portsmouth is 13.9h.

Sunshine

Months with the most sunshine are June through August, with an average of 9h of sunshine.

UV index

The average daily maximum UV index in Portsmouth is 7. A UV Index estimate of 6 to 7 represents a high health vulnerability from unsafe exposure to the UV radiation for average individuals.
Note: In August, the average maximum UV index of 7 translate into the following recommendations:
Take precautions against overexposure. Fair-skinned people may get burned in less than 20 minutes. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.

What is the temperature in August in Portsmouth?

In Portsmouth, in August, the average high-temperature is 77°F (25°C), and the average low-temperature is 59°F (15°C).

How much does it rain in Portsmouth in August?

In Portsmouth, New Hampshire, in August, it is raining for 10 days, with typically 2.8" (70mm) of accumulated precipitation.

What is the driest month in Portsmouth?

The month with the least rainfall in Portsmouth is August when the rain falls for 10 days and typically collects 2.8" (70mm) of precipitation.

When is the ocean warmest in Portsmouth?

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

What is the ocean temperature in August in Portsmouth?

In Portsmouth, New Hampshire, the average seawater temperature in August is 65.7°F (18.7°C). Swimming in 65.7°F (18.7°C) is not enjoyable for the majority. Controlling breathing becomes progressively more difficult as surface water temperature decreases below 69.8°F (21°C).

How many hours of daylight does Portsmouth have in August?

In August, the average length of the day is 13.9h.

What is the month with the most sunshine in Portsmouth?

June through August, with an average of 9h of sunshine, are months with the most sunshine.

How many hours of sunshine does Portsmouth have in August?

In Portsmouth, the average sunshine in August is 9h.

What is the UV index intensity in August in Portsmouth?

In Portsmouth, the average daily maximum UV index in August is 7. A UV Index of 6 to 7 symbolizes a high health vulnerability from the exposure to the Sun's UV rays.
Average temperature in August - Portsmouth, NH
  • Average high temperature in August: 77°F

The warmest month (with the highest average high temperature) is July (79°F).
Months with the lowest average high temperature are January and February (32°F).

  • Average low temperature in August: 59°F

The month with the highest average low temperature is July (61°F).
The coldest month (with the lowest average low temperature) is January (16°F).

Average rainfall in August - Portsmouth, NH
  • Average rainfall in August: 2.8"

The wettest month (with the highest rainfall) is November (4.9").
The driest month (with the lowest rainfall) is August (2.8").

Average rainfall days in August - Portsmouth, NH
  • Average rainfall days in August: 10 days

Months with the highest number of rainy days are May and December (12 days).
The month with the lowest number of rainy days is September (8 days).

Average sea temperature in August - Portsmouth, NH
  • Average sea temperature in August: 65.6°F

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).

Average daylight in August / Average sunshine in August - Portsmouth, NH
  • Average daylight in August: 13.9h

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

  • Average sunshine in August: 9h

Months with most sunshine are June, July and August (Average sunshine: 9h).
Months with least sunshine are January, November and December (Average sunshine: 5).

Average UV index in August - Portsmouth, NH
  • Average UV index in August: 7

Months with the highest UV index are June and July (UV index 8).
Months with the lowest UV index are January and December (UV index 1).