Climate and monthly weather forecastPortsmouth, RI
Climate and monthly weather forecast
The climate of Portsmouth
Portsmouth, Rhode Island is categorized under the Köppen climate classification as Cfa also known as Humid subtropical with no dry season. Geographically, Portsmouth is located in the northern hemisphere thus, physically confirming to four distinct seasons - spring, summer, autumn, and winter.Throughout the year, temperature sway is observed, starting from a minimum of about 26.4°F (-3.1°C) in the cold winter months and escalating progressively to reach a peak of about 78.3°F (25.7°C) during the heat of summer. The relative humidity generally hovers around 75% to 81% all year, providing a damp feeling most of the year. However, recorded rainfall - ranging from 1.42" (36mm) to 3.27" (83mm) - makes its presence felt across all seasons. The months experiencing the most significant rainfall count are generally April and November.
The region experiences unique weather patterns, with January being the coldest month and July being the warmest. Snowfall is a rarity, with nominal traces found only in January, March, and November. Sunshine plays a pivotal role, spanning the widest difference from 4.8 hours in February to 10.5 hours in August, creating varied environmental set-ups for residents and visitors alike.
Interestingly, Portsmouth is also influenced by wind conditions. Typically, the average wind speed leans from 8.1mph (13km/h) to 12.1mph (19.5km/h), with the highest wind gust occurring mostly during the winter months when it can peak up to 17.9mph (28.8km/h).
The best time to visit Portsmouth
Given the variables, the most agreeable time to visit Portsmouth hinges primarily on individual preferences for selected weather conditions. However, May through August proves to be delightful for those bidding for warm temperatures paired with ample sunshine hours. This duration is amicable for outdoor activities, with temperatures averaging between 53.2°F (11.8°C) to 78.3°F (25.7°C) coupled with up to 10.5 hours of daily sunshine. Rainfall is relatively consistent, alternating around 2" (51mm) per month, creating no significant hindrance.The worst time to visit Portsmouth
The disadvantageous time to plan a trip to Portsmouth is predominantly during the cold season. December through February sees the temperatures dipping low, ranging from 26.4°F (-3.1°C) to 37.9°F (3.3°C). Furthermore, these months offer the least sunshine hours, dropping to as low as 4.9 hours daily in December. Although rainfall remains consistent, the presence of snow on certain days further strengthens the adverse weather conditions for visitors.Spring weather in Portsmouth
Spring unfolds in Portsmouth from March to May. Rising from the winter slump, temperature begins to ascend, transitioning from 33.1°F (0.6°C) in March and culminating to 62.6°F (17°C) in May. As the season advances, daylight hours increase from 12 hours in March to 14.5 hours in May, enhancing the overall pleasant ambiance. However, be wary of precipitation, as this season receives the highest rainfall, peaking in April at 2.95" (75mm).Summer weather in Portsmouth
Summer in Portsmouth spans from June through August, showcasing the best of weather parameters. Temperatures peak and oscillate around 70.5°F (21.4°C) to 78.3°F (25.7°C), offering the much-needed warmth. Multiple sunshine hours peaking at 10.5 hours in August further adds to the luminosity of the season. Rainfall calms down to accommodate favorable weather conditions. Consequently, summer months record a lesser cloud coverage, encouraging various outdoor activities.Autumn weather in Portsmouth
Autumn comes to Portsmouth in September and lasts through November. The departure of summer leads to a gradual decline in temperature, sliding from 71.4°F (21.9°C) in September to 51.1°F (10.6°C) in November. Though daylight hours shrink alongside, there is still fair light available, approximately around 9.9 hours by November. Interestingly, rainfall extends its generosity to this season, making November the wettest month with a high of 3.27" (83mm).Winter weather in Portsmouth
Winter in Portsmouth is characterized by cold temperatures, dialed sunlight hours and occasional snowfall. The chilling season stretches from December through February. The temperature goes through an ebbed phase ranging from 26.4°F (-3.1°C) to 37.9°F (3.3°C). Amidst the restrained daylight hours dwindling to about 9.2 hours by the end of February, residents and descendants witness peculiar instances of snowfall, especially in January and February. The phenomenon, although modest, adds to the charisma of the severe season in Portsmouth.Weather in January
January brings with it the coldest spell of the year in Portsmouth, Rhode Island, with the mercury dipping to a chilly low of 26.4°F (-3.1°C). A major shift from the frosty conditions is not expected in February as cold weather will continue to hold a firm grip on the city. Weather in January »Weather in February
February inches the temperature scale upwards a bit, providing Portsmouth's residents with mild relief from January's biting cold. Lingering snow showers from the previous month peter out, leading to decreased snowfall. Expect temperatures to rise significantly in March with the onset of spring. Weather in February »Weather in March
The arrival of March in Portsmouth heralds the commencement of spring, seeing a jump in temperatures from the February chill. March can also count itself as one of the windiest months with winds blowing at an average speed of 11.9mph (19.2km/h). Weather in March »Weather in April
April's temperatures in Portsmouth make a substantial leap upwards from March, making the residents relish the heartening spring weather even more. While the frequency of rainfall remains generally constant, an interesting weather pattern to note is the increased number of rainy days. Weather in April »Weather in May
May embraces Portsmouth with a marked rise in temperature, making the month particularly enjoyable for outdoor activities. A dip in rainfall distinguishes this month, with precipitation significantly lower than in the preceding month, promising opportunities for sun-soaked adventures. Weather in May »Weather in June
June in Portsmouth, Rhode Island, introduces the locals and tourists to the official start of summer. Temperatures peak to an average high of 70.5°F (21.4°C), setting the stage for a warm July. Though rainfall gets a minor boost, the number of rainy days remains comparable to May. Weather in June »Weather in July
July holds the torch as the warmest month in Portsmouth with an average high temperature soaring to 78.3°F (25.7°C). The upward progression of temperature is halted in August with the peak summer month mirroring July's gap. Although clear skies dominate most of the month, brief spells of rain fill up the dry spells in the otherwise hot days. Weather in July »Weather in August
August maintains the summer sizzle in Portsmouth with little to no drop in temperature from July. Rainfall sees a minute rise compared to July, but overall, the fair weather continues to prevail. The approaching September brings a relief in the form of a moderate drop in temperature. Weather in August »Weather in September
September marks the start of a transitional phase in Portsmouth as summer heat gives way to relatively cooler autumn temperatures. Warm days from the summer month of August become cooler, contributing to the overall pleasant weather. Weather in September »Weather in October
October typically signifies the arrival of fall in Portsmouth where temperatures experience a noticeable dip from September. An upsurge in rainfall, peaking at 3.27" (83mm), makes it the rainiest month of the year. November will continue the trend, with similar patterns of cool temperature and rain. Weather in October »Weather in November
November brings significantly cooler temperatures to Portsmouth, hinting at the imminent approach of winter. The crisp air and falling leaves echo the quintessential New England autumn. A decrease in rainfall from the previous month sets the stage for drier winter months ahead. Weather in November »Weather in December
December in Portsmouth, Rhode Island signifies the return of winter with temperatures dropping considerably from those in November. The harsh cold is accompanied by the highest amount of rainfall for the year, reaching up to 3.23" (82mm). Weather in December »Updated: Jul 30, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Portsmouth's temperature records reveal January as the coldest month, marked by average highs of 36.1°F (2.3°C) and lows of 26.4°F (-3.1°C).
In Portsmouth, during the entire year, the rain falls for 148.1 days and collects up to 29.65" (753mm) of precipitation.
January through March, May, November and December are months with snowfall.
In Portsmouth, during the entire year, snow falls for 22.9 days and aggregates up to 8.78" (223mm) of snow.
The months with the lowest UV index are January through March and December, with an average maximum UV index of 2.
The month with the most snowfall is February, when snow falls for 6.2 days and typically aggregates up to 2.76" (70mm) of snow.
February has the least sunshine of the year, with an average of 4.8h of sunshine.
The least humid month is March, with an average relative humidity of 73%.
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts, and the time zone changes from EST to EDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from EDT to EST.
In Portsmouth, snow does not fall in April, June through October.
The most humid month is June, with an average relative humidity of 81%.
The month with the longest days is June, with an average of 15h and 6min of daylight.
The months with the highest UV index are June through August, with an average maximum UV index of 6.
Portsmouth's July weather, with an average high temperature of 78.3°F (25.7°C) and an average low temperature of 66.7°F (19.3°C), tends to be the warmest of the year.
August has the most sunshine of the year, with an average of 10.5h of sunshine.
September is the month with the least rainfall in Portsmouth. Rain falls for 11.6 days and accumulates 1.42" (36mm) of precipitation.
The month with the most rainfall is October, when the rain falls for 13.4 days and typically aggregates up to 3.27" (83mm) of precipitation.
The month with the shortest days is December, with an average of 9h and 12min of daylight.
Average temperature
Portsmouth, RI
The warmest month (with the highest average high temperature) is July (78.3°F).
The month with the lowest average high temperature is January (36.1°F).
The month with the highest average low temperature is July (66.7°F).
The coldest month (with the lowest average low temperature) is January (26.4°F).
Average pressure
Portsmouth, RI
- Average pressure in January:
30.01"Hg - Average pressure in February:
29.99"Hg - Average pressure in March:
30.03"Hg - Average pressure in April:
29.98"Hg - Average pressure in May:
30.01"Hg - Average pressure in June:
29.93"Hg
- Average pressure in July:
29.95"Hg - Average pressure in August:
29.98"Hg - Average pressure in September:
30.05"Hg - Average pressure in October:
30.01"Hg - Average pressure in November:
30.07"Hg - Average pressure in December:
30.03"Hg
The month with the highest atmospheric pressure is November (30.07"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed
Portsmouth, RI
- Average wind speed in January:
12.1mph - Average wind speed in February:
11.9mph - Average wind speed in March:
11.9mph - Average wind speed in April:
11.1mph - Average wind speed in May:
9.6mph - Average wind speed in June:
8.8mph
- Average wind speed in July:
8.3mph - Average wind speed in August:
8.1mph - Average wind speed in September:
9mph - Average wind speed in October:
10.6mph - Average wind speed in November:
11.2mph - Average wind speed in December:
11.6mph
The windiest month (with the highest average wind speed) is January (12.1mph).
The calmest month (with the lowest average wind speed) is August (8.1mph).
Average humidity
Portsmouth, RI
The month with the highest relative humidity is June (81%).
The month with the lowest relative humidity is March (73%).
Average rainfall
Portsmouth, RI
- Average rainfall in January:
2.6" - Average rainfall in February:
2.36" - Average rainfall in March:
2.83" - Average rainfall in April:
2.95" - Average rainfall in May:
2.09" - Average rainfall in June:
2.44"
- Average rainfall in July:
2.01" - Average rainfall in August:
2.09" - Average rainfall in September:
1.42" - Average rainfall in October:
3.27" - Average rainfall in November:
2.36" - Average rainfall in December:
3.23"
The wettest month (with the highest rainfall) is October (3.27").
The driest month (with the least rainfall) is September (1.42").
Average rainfall days
Portsmouth, RI
- Average rainfall days in January:
8.3 days - Average rainfall days in February:
9.4 days - Average rainfall days in March:
12.1 days - Average rainfall days in April:
15.6 days - Average rainfall days in May:
14.8 days - Average rainfall days in June:
14.5 days
- Average rainfall days in July:
14.5 days - Average rainfall days in August:
11.8 days - Average rainfall days in September:
11.6 days - Average rainfall days in October:
13.4 days - Average rainfall days in November:
10.6 days - Average rainfall days in December:
11.5 days
The month with the highest number of rainy days is April (15.6 days).
The month with the least rainy days is January (8.3 days).
Average snowfall
Portsmouth, RI
The month with the highest snowfall is February (2.76").
The months with the least snowfall are April, June, July, August, September and October (0").
Average snowfall days
Portsmouth, RI
- Average snowfall days in January:
6.6 days - Average snowfall days in February:
6.2 days - Average snowfall days in March:
5.2 days - Average snowfall days in April:
0.2 days - Average snowfall days in May:
0.2 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0 days - Average snowfall days in October:
0 days - Average snowfall days in November:
0.7 days - Average snowfall days in December:
3.8 days
The month with the highest number of snowfall days is January (6.6 days).
The months with the least snowfall days are June, July, August, September and October (0 days).
Average daylight / Average sunshine
Portsmouth, RI
- Average daylight in January:
9h and 36min - Average daylight in February:
10h and 36min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 24min - Average daylight in May:
14h and 30min - Average daylight in June:
15h and 6min
- Average daylight in July:
14h and 48min - Average daylight in August:
13h and 48min - Average daylight in September:
12h and 30min - Average daylight in October:
11h and 6min - Average daylight in November:
9h and 54min - Average daylight in December:
9h and 12min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in January:
5h and 12min - Average sunshine in February:
4h and 48min - Average sunshine in March:
6h and 0min - Average sunshine in April:
8h and 18min - Average sunshine in May:
8h and 30min - Average sunshine in June:
9h and 12min
- Average sunshine in July:
10h and 18min - Average sunshine in August:
10h and 30min - Average sunshine in September:
8h and 42min - Average sunshine in October:
6h and 18min - Average sunshine in November:
5h and 24min - Average sunshine in December:
4h and 54min
The month with the most sunshine is August (Average sunshine: 10h and 30min).
The month with the least sunshine is February (Average sunshine: 4h and 48min).
Average sunshine days
Portsmouth, RI
- Average sunshine days in January:
15.6 days - Average sunshine days in February:
14 days - Average sunshine days in March:
14.4 days - Average sunshine days in April:
12.3 days - Average sunshine days in May:
14.9 days - Average sunshine days in June:
13.4 days
- Average sunshine days in July:
14.7 days - Average sunshine days in August:
16.9 days - Average sunshine days in September:
15.8 days - Average sunshine days in October:
15.1 days - Average sunshine days in November:
17.7 days - Average sunshine days in December:
15.5 days
The month with the most sunshine days is November (17.7 days).
The month with the least sunshine days is April (12.3 days).
Average UV index
Portsmouth, RI
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, March and December (UV index 2).
Average cloud cover
Portsmouth, RI
The month with the most cloud cover is March (Cloud cover 48).
The month with the least cloud cover is August (Cloud cover 29).
Average visibility
Portsmouth, RI
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
