Climate and Average Weather Year Round in Portsmouth Virginia, United States

In Portsmouth, the summers are muggy and hot, the winters are very cold and windy, and it is wet and partly cloudy year round. Over the course of the year, the temperature typically varies from 34°F to 88°F and is rarely below 22°F or above 95°F.

Based on the tourism score, the best times of year to visit Portsmouth for warm-weather activities are from mid to late May and from late August to mid October.

The hot season lasts for 3.5 months, from May 30 to September 15, with an average daily high temperature above 81°F. The hottest month of the year in Portsmouth is July, with an average high of 88°F and low of 72°F.

The cool season lasts for 3.0 months, from December 4 to March 5, with an average daily high temperature below 57°F. The coldest month of the year in Portsmouth is January, with an average low of 34°F and high of 50°F.

In Portsmouth, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year in Portsmouth begins around August 7 and lasts for 3.6 months, ending around November 24.

The clearest month of the year in Portsmouth is October, during which on average the sky is clear, mostly clear, or partly cloudy 64% of the time.

The cloudier part of the year begins around November 24 and lasts for 8.5 months, ending around August 7.

The cloudiest month of the year in Portsmouth is January, during which on average the sky is overcast or mostly cloudy 49% of the time.

© OpenStreetMap contributors

Compare Portsmouth to:

CompareMap

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Portsmouth varies throughout the year.

The wetter season lasts 3.6 months, from May 11 to August 29, with a greater than 33% chance of a given day being a wet day. The month with the most wet days in Portsmouth is July, with an average of 13.3 days with at least 0.04 inches of precipitation.

The drier season lasts 8.4 months, from August 29 to May 11. The month with the fewest wet days in Portsmouth is November, with an average of 6.7 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Portsmouth is July, with an average of 13.3 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 45% on August 4.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Portsmouth experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year in Portsmouth. The month with the most rain in Portsmouth is August, with an average rainfall of 4.5 inches.

The month with the least rain in Portsmouth is February, with an average rainfall of 2.9 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Portsmouth experiences some seasonal variation in monthly snowfall.

The snowy period of the year lasts for 2.4 months, from December 26 to March 5, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Portsmouth is February, with an average snowfall of 2.0 inches.

The snowless period of the year lasts for 9.6 months, from March 5 to December 26. The least snow falls around July 13, with an average total accumulation of 0.0 inches.

The length of the day in Portsmouth varies significantly over the course of the year. In 2026, the shortest day is December 21, with 9 hours, 38 minutes of daylight; the longest day is June 21, with 14 hours, 41 minutes of daylight.

The earliest sunrise is at 5:45 AM on June 13, and the latest sunrise is 1 hour, 43 minutes later at 7:28 AM on October 31. The earliest sunset is at 4:48 PM on December 6, and the latest sunset is 3 hours, 40 minutes later at 8:28 PM on June 28.

Daylight saving time (DST) is observed in Portsmouth during 2026, starting in the spring on March 8, lasting 7.8 months, and ending in the fall on November 1.

The figure below presents a compact representation of key lunar data for 2026. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

Portsmouth experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 4.5 months, from May 20 to October 6, during which time the comfort level is muggy, oppressive, or miserable at least 21% of the time. The month with the most muggy days in Portsmouth is July, with 25.1 days that are muggy or worse.

The month with the fewest muggy days in Portsmouth is February, with 0.0 days that are muggy or worse.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Portsmouth experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 7.3 months, from October 6 to May 14, with average wind speeds of more than 10.0 miles per hour. The windiest month of the year in Portsmouth is March, with an average hourly wind speed of 11.7 miles per hour.

The calmer time of year lasts for 4.7 months, from May 14 to October 6. The calmest month of the year in Portsmouth is July, with an average hourly wind speed of 8.3 miles per hour.

The predominant average hourly wind direction in Portsmouth varies throughout the year.

The wind is most often from the south for 4.7 months, from March 31 to August 23, with a peak percentage of 39% on July 30. The wind is most often from the east for 4.0 weeks, from August 23 to September 20, with a peak percentage of 33% on September 7. The wind is most often from the north for 6.4 months, from September 20 to March 31, with a peak percentage of 36% on January 1.

Portsmouth is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences significant seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.7 months, from June 13 to October 2, with an average temperature above 71°F. The month of the year in Portsmouth with the warmest water is August, with an average temperature of 78°F.

The time of year with cooler water lasts for 3.4 months, from December 21 to April 3, with an average temperature below 50°F. The month of the year in Portsmouth with the coolest water is February, with an average temperature of 43°F.

To characterize how pleasant the weather is in Portsmouth throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best times of year to visit Portsmouth for general outdoor tourist activities are from mid to late May and from late August to mid October, with a peak score in the last week of September.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Portsmouth for hot-weather activities is from mid June to mid September, with a peak score in the last week of August.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Portsmouth typically lasts for 8.3 months (254 days), from around March 16 to around November 25, rarely starting before February 25 or after April 3, and rarely ending before November 7 or after December 16.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms in Portsmouth should appear around February 18, only rarely appearing before January 27 or after March 12.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.

The brighter period of the year lasts for 4.0 months, from April 17 to August 18, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest month of the year in Portsmouth is June, with an average of 6.8 kWh.

The darker period of the year lasts for 3.0 months, from November 8 to February 8, with an average daily incident shortwave energy per square meter below 3.2 kWh. The darkest month of the year in Portsmouth is December, with an average of 2.3 kWh.

For the purposes of this report, the geographical coordinates of Portsmouth are 36.835 deg latitude, -76.298 deg longitude, and 7 ft elevation.

The topography within 2 miles of Portsmouth is essentially flat, with a maximum elevation change of 16 feet and an average elevation above sea level of 5 feet. Within 10 miles is essentially flat (102 feet). Within 50 miles also contains only modest variations in elevation (190 feet).

The area within 2 miles of Portsmouth is covered by artificial surfaces (88%) and water (12%), within 10 miles by artificial surfaces (66%) and water (15%), and within 50 miles by water (41%) and trees (24%).