September weather forecastAltoona, IA
September
Weather in September
September introduces subtle autumn vibes to Altoona weather, with average temperatures dropping to 75.4°F (24.1°C). Despite being the start of fall, occasional spells of warmth from the preceding summer persist. The frequency of rainfall remains moderate, ensuring the city's greenery remains vibrant. With the falling temperature, daylight hours also diminish but there is still enough sunlight to enjoy various outdoor activities. The gradual change in weather and leaf coloration offer a preview of the impending fall season.Temperature
September witnesses a gentle descent in average high-temperature, descending from August's moderately hot 81.1°F (27.3°C) to a still warm 75.4°F (24.1°C). Altoona sees an average low-temperature of 55.9°F (13.3°C) during September.Humidity
The average relative humidity in September is 76%.Rainfall
In Altoona, in September, during 7.2 rainfall days, 0.63" (16mm) of precipitation is typically accumulated. Throughout the year, there are 79 rainfall days, and 5.94" (151mm) of precipitation is accumulated.Snowfall
In Altoona, snow does not fall in May through September.Daylight
In September, the average length of the day in Altoona is 12h and 28min.On the first day of September, sunrise is at 6:40 am and sunset at 7:46 pm. On the last day of the month, sunrise is at 7:10 am and sunset at 6:56 pm CDT.
Sunshine
In September, the average sunshine is 9.4h.UV index
In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a moderate health risk from exposure to the Sun's UV rays for the ordinary person.Note: The average daily UV index of 4 in September transforms into the following instructions:
Be vigilant - A duty to shield skin and eyes from injury exists. Given the potency of the midday Sun's UV radiation, one should avoid prolonged exposure. Prioritize a wide-brim hat for comprehensive sun defense for your face, neck, eyes, and ears.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Altoona, IA
- Average high temperature in September: 75.4°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (27.5°F).
- Average low temperature in September: 55.9°F
The month with the highest average low temperature is July (65.1°F).
The coldest month (with the lowest average low temperature) is January (14.4°F).
Average pressure in September
Altoona, IA
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Altoona, IA
- Average wind speed in September: 8mph
The windiest month (with the highest average wind speed) is April (10.4mph).
The calmest month (with the lowest average wind speed) is August (6.9mph).
Average humidity in September
Altoona, IA
- Average humidity in September: 76%
The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is October (70%).
Average rainfall in September
Altoona, IA
- Average rainfall in September: 0.63"
The wettest month (with the highest rainfall) is May (0.98").
The driest months (with the least rainfall) are January, February and December (0.24").
Average rainfall days in September
Altoona, IA
- Average rainfall days in September: 7.2 days
The month with the highest number of rainy days is May (11.6 days).
The month with the least rainy days is January (1.8 days).
Average snowfall in September
Altoona, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (0.91").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Altoona, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (6.2 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Altoona, IA
- Average daylight in September: 12h and 30min
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 24min
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 12min).
Average sunshine days in September
Altoona, IA
- Average sunshine days in September: 21 days
The month with the most sunshine days is December (25.5 days).
The month with the least sunshine days is June (15.5 days).
Average UV index in September
Altoona, IA
- Average UV index in September: 4
The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in September
Altoona, IA
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 54).
The months with the least cloud cover are July and September (Cloud cover 29).
Average visibility in September
Altoona, IA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are July and August (5mi).
