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

May 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
The last month of the spring, May, is a comfortable month in Portsmouth, New Hampshire, with average temperature ranging between max 64°F (17.8°C) and min 45°F (7.2°C).

Temperature

In Portsmouth, the average high-temperature in May rises, from a cool 52°F (11.1°C) in April, to an enjoyable 64°F (17.8°C). In Portsmouth, in May, the average low-temperature is 45°F (7.2°C).

Rainfall

In Portsmouth, New Hampshire, in May, it is raining for 12 days, with typically 3.4" (86mm) of accumulated precipitation. In Portsmouth, during the entire year, the rain falls for 125 days and collects up to 42.4" (1078mm) of precipitation.

Ocean temperature

In Portsmouth, the average water temperature is 47.3°F (8.5°C). At temperatures below 50°F (10°C), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 55.4°F (13°C) is not comfortable.

Daylight

The average length of the day in Portsmouth is 14.7h.

Sunshine

In Portsmouth, the average sunshine is 8h.

UV index

In Portsmouth, the average daily maximum UV index in May is 7. A UV Index reading of 6 to 7 represents a high health hazard from unsafe exposure to the UV radiation for average individuals.
The daily maximum UV index of 7 in May interpret into the following advice:
Take precautions against overexposure. Protection against sun damage is needed. 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 May in Portsmouth?

The average high-temperature, in May, is 64°F (17.8°C), while the average low-temperature is 45°F (7.2°C).

How many days does it rain in May in Portsmouth?

In Portsmouth, New Hampshire, in May, it is raining for 12 days, with typically 3.4" (86mm) of accumulated precipitation.

How cold is the water in May in Portsmouth?

In Portsmouth, the average seawater temperature in May is 47.3°F (8.5°C). Swimming in 47.3°F (8.5°C) is considered life-threatening. Even a few minutes in 55.4°F (13°C) water is uncomfortable, and swimming below 50°F (10°C) may cause total loss of breathing control and cold shock, depending on a person's physique.

What is the average length of the day in May in Portsmouth?

In Portsmouth, New Hampshire, the average length of the day in May is 14.7h.

How long on average sun shines in May in Portsmouth?

In Portsmouth, New Hampshire, the average sunshine in May is 8h.

How high is the UV index in May in Portsmouth?

In May, the average daily maximum UV index in Portsmouth, New Hampshire, is 7. A UV Index value of 6 to 7 symbolizes a high health threat from the exposure to the Sun's UV rays.
Average temperature in May - Portsmouth, NH
  • Average high temperature in May: 64°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 May: 45°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 May - Portsmouth, NH
  • Average rainfall in May: 3.4"

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 May - Portsmouth, NH
  • Average rainfall days in May: 12 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 May - Portsmouth, NH
  • Average sea temperature in May: 47.3°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 May / Average sunshine in May - Portsmouth, NH
  • Average daylight in May: 14.7h

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 May: 8h

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 May - Portsmouth, NH
  • Average UV index in May: 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).