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 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
Alton's weather subtly changes with the onset of September, barely falling from a warm 77.2°F (25.1°C) in August to a pleasant 69.6°F (20.9°C). Throughout the month of September, the average temperature dips to a frosty 49.6°F (9.8°C) at night.Humidity
In September, the average relative humidity is 80%.Rainfall
September is the month with the least rainfall. Rain falls for 10.8 days and accumulates 1.61" (41mm) of precipitation.Snowfall
In Alton, snow does not fall in June through September.Daylight
In Alton, the average length of the day in September is 12h and 29min.On the first day of the month, sunrise is at 6:09 am and sunset at 7:19 pm. On the last day of September, sunrise is at 6:42 am and sunset at 6:27 pm EDT.
Sunshine
In September, the average sunshine is 8.2h.UV index
In September, the average daily maximum UV index is 3. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for average individuals.Note: The maximum UV index of 3 during September leads to these instructions:
Be vigilant - A duty to shield skin and eyes from injury exists. Being exposed to the midday Sun can have harmful effects due to strong UV radiation; always take precautions. Tightly woven clothing, when worn loosely, shields effectively against the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in September?
What is the average humidity in September?
What is the driest month?
How many days does it rain in September?
When it does not snow?
Does it snow in September?
What is the average length of the day in September?
When is the sunrise / sunset in September?
How long on average sun shines in September in Alton?
What is the UV index reading in September?
Average temperature in September
Alton, NH
- Average high temperature in September: 69.6°F
The warmest month (with the highest average high temperature) is July (78.3°F).
The month with the lowest average high temperature is January (26.1°F).
- Average low temperature in September: 49.6°F
The month with the highest average low temperature is July (57.6°F).
The coldest month (with the lowest average low temperature) is January (12.9°F).
Average pressure in September
Alton, 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 (29.91"Hg).
Average wind speed in September
Alton, NH
- Average wind speed in September: 4.8mph
The windiest months (with the highest average wind speed) are January and February (7.1mph).
The calmest months (with the lowest average wind speed) are July and August (4.7mph).
Average humidity in September
Alton, NH
- Average humidity in September: 80%
The months with the highest relative humidity are January and February (86%).
The month with the lowest relative humidity is April (76%).
Average rainfall in September
Alton, NH
- Average rainfall in September: 1.61"
The wettest month (with the highest rainfall) is October (3.19").
The driest month (with the least rainfall) is September (1.61").
Average rainfall days in September
Alton, NH
- Average rainfall days in September: 10.8 days
The month with the highest number of rainy days is April (15.8 days).
The month with the least rainy days is February (8.3 days).
Average snowfall in September
Alton, NH
- Average snowfall in September: 0"
The month with the highest snowfall is February (9.84").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Alton, NH
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (13.2 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Alton, NH
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).
- Average sunshine in September: 8h and 1min
The month with the most sunshine is August (Average sunshine: 10h and 12min).
The month with the least sunshine is February (Average sunshine: 4h and 30min).
Average sunshine days in September
Alton, NH
- Average sunshine days in September: 16.9 days
The month with the most sunshine days is September (16.9 days).
The month with the least sunshine days is April (11.4 days).
Average UV index in September
Alton, NH
- Average UV index in September: 3
The months with the highest UV index are June, July and August (UV index 5).
The months with the lowest UV index are January, February, March, October, November and December (UV index 2).
Average cloud cover in September
Alton, NH
- Average cloud cover in September: 39
The month with the most cloud cover is March (Cloud cover 52).
The month with the least cloud cover is August (Cloud cover 35).
Average visibility in September
Alton, NH
- Average visibility in September: 4mi
The months with the highest visibility are January, March, April, May, June, July, August, October, November and December (5mi).
The months with the lowest visibility are February and September (4mi).
Alton, New Hampshire, USA
Weather forecast for your location
2. Allow the app to use your location