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
Portsmouth's transition from August to September introduces an average high-temperature of a still warm 75°F (23.9°C), marking an insignificant variation from the 80.2°F (26.8°C). September nights observe an average temperature dip to a mild 55.9°F (13.3°C).Humidity
In Portsmouth, the average relative humidity in September is 75%.Rainfall
In Portsmouth, in September, during 10.5 rainfall days, 1.65" (42mm) of precipitation is typically accumulated. In Portsmouth, during the entire year, the rain falls for 113.5 days and collects up to 15.71" (399mm) of precipitation.Snowfall
In Portsmouth, snow does not fall in June through September.Daylight
The average length of the day in September is 12h and 28min.On the first day of September, sunrise is at 6:48 am and sunset at 7:54 pm. On the last day of the month, sunrise is at 7:18 am and sunset at 7:04 pm CDT.
Sunshine
In Portsmouth, the average sunshine in September is 9.1h.UV index
In September, the average daily maximum UV index in Portsmouth is 4. A UV Index reading of 3 to 5 represents a moderate health risk from unsafe exposure to UV radiation for the average person.Note: A typical high UV index of 4 in September suggests the following recommendations:
Adopt protective measures - It is advised to guard against sun damage. Direct exposure to the Sun during its peak hours around mid-day should be minimized for safety. For optimum UV protection, wear sun-resistant attire complemented with a hat and quality shades.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the temperature in September?
What is the average humidity in September in Portsmouth?
How much does it rain in September?
When it does not snow?
Does it snow in Portsmouth 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?
How high is the UV index in September in Portsmouth?
Average temperature in September
Portsmouth, IA
- Average high temperature in September: 75°F
The warmest month (with the highest average high temperature) is July (82.6°F).
The month with the lowest average high temperature is January (27.3°F).
- Average low temperature in September: 55.9°F
The month with the highest average low temperature is July (64.9°F).
The coldest month (with the lowest average low temperature) is January (14.5°F).
Average pressure in September
Portsmouth, IA
- Average pressure in September: 30"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.87"Hg).
Average wind speed in September
Portsmouth, IA
- Average wind speed in September: 8.5mph
The windiest month (with the highest average wind speed) is April (10.9mph).
The calmest month (with the lowest average wind speed) is July (7.2mph).
Average humidity in September
Portsmouth, IA
- Average humidity in September: 75%
The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is October (68%).
Average rainfall in September
Portsmouth, IA
- Average rainfall in September: 1.65"
The wettest month (with the highest rainfall) is June (2.64").
The driest month (with the least rainfall) is January (0.43").
Average rainfall days in September
Portsmouth, IA
- Average rainfall days in September: 10.5 days
The month with the highest number of rainy days is June (16.1 days).
The month with the least rainy days is February (2.8 days).
Average snowfall in September
Portsmouth, IA
- Average snowfall in September: 0"
The month with the highest snowfall is February (2.09").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Portsmouth, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (8.3 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Portsmouth, IA
- Average daylight in September: 12h and 3min
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 September: 9h and 1min
The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 30min).
Average sunshine days in September
Portsmouth, IA
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is December (21.6 days).
The month with the least sunshine days is June (11.4 days).
Average UV index in September
Portsmouth, IA
- Average UV index in September: 4
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, October, November and December (UV index 2).
Average cloud cover in September
Portsmouth, IA
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 52).
The month with the least cloud cover is July (Cloud cover 27).
Average visibility in September
Portsmouth, IA
- 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, Iowa, USA
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