Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average sea temperature in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
The start of September comes with a small reduction in the average high-temperature, subtly receding from a moderately hot 75.7°F (24.3°C) in August to an agreeable 69.1°F (20.6°C). In the month of September, Portsmouth witnesses a consistent average low-temperature of 56.1°F (13.4°C).Humidity
In September, the average relative humidity is 79%.Rainfall
September is the month with the least rainfall. Rain falls for 11.3 days and accumulates 1.54" (39mm) of precipitation.Snowfall
May through September are months without snowfall.Ocean temperature
In Portsmouth, in September, the average water temperature is 61.9°F (16.6°C).Note: A majority do not enjoy swimming in water at 61.9°F (16.6°C). The difficulty in controlling breathing increases progressively as the temperature dips below 69.8°F (21°C).
Daylight
In Portsmouth, the average length of the day in September is 12h and 29min.On the first day of the month, sunrise is at 6:08 am and sunset at 7:17 pm. On the last day of September, sunrise is at 6:40 am and sunset at 6:25 pm EDT.
Sunshine
The average sunshine in September is 8.6h.UV index
In Portsmouth, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate health risk from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The daily high UV index of 4 during September translates into the following recommendations:
Preventative actions are necessary - The mandate to avoid skin and eye damage is in place. The best time to avoid the Sun's harmful UV radiation is during midday when it's most potent. Sun-related eye harm can be minimized with proper sunglasses offering UVA and UVB coverage.
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Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in September?
What is the average humidity in September in Portsmouth?
What is the driest month?
How many days does it rain in September?
When it does not snow?
Does it snow in September?
How cold is the water in September?
How many hours of daylight does Portsmouth have in September?
When are sunrise and sunset in September?
How long on average sun shines in September?
What is the UV index intensity in September?
Average temperature in September
Portsmouth, NH
- Average high temperature in September: 69.1°F
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).
- Average low temperature in September: 56.1°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).
Average pressure in September
Portsmouth, NH
- Average pressure in September: 30.05"Hg
The month with the highest atmospheric pressure is November (30.06"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in September
Portsmouth, NH
- Average wind speed in September: 7.6mph
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).
Average humidity in September
Portsmouth, NH
- Average humidity in September: 79%
The month with the highest relative humidity is June (80%).
The months with the lowest relative humidity are April and November (75%).
Average rainfall in September
Portsmouth, NH
- Average rainfall in September: 1.54"
The wettest month (with the highest rainfall) is October (2.83").
The driest month (with the least rainfall) is September (1.54").
Average rainfall days in September
Portsmouth, NH
- Average rainfall days in September: 11.3 days
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).
Average snowfall in September
Portsmouth, NH
- Average snowfall in September: 0"
The month with the highest snowfall is January (4.02").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Portsmouth, NH
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (8.8 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average sea temperature in September
Portsmouth, NH
- Average sea temperature in September: 61.9°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 September /
Average sunshine in September
Portsmouth, NH
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).
- Average sunshine in September: 8h and 4min
The month with the most sunshine is August (Average sunshine: 10h and 36min).
The months with the least sunshine are February and December (Average sunshine: 4h and 48min).
Average sunshine days in September
Portsmouth, NH
- Average sunshine days in September: 16.8 days
The month with the most sunshine days is September (16.8 days).
The month with the least sunshine days is April (13.2 days).
Average UV index in September
Portsmouth, NH
- Average UV index in September: 4
The months with the highest UV index are July and August (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in September
Portsmouth, NH
- Average cloud cover in September: 33
The month with the most cloud cover is March (Cloud cover 50).
The month with the least cloud cover is August (Cloud cover 29).
Average visibility in September
Portsmouth, NH
- Average visibility in September: 6mi
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).
Portsmouth, New Hampshire, USA
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