September weather forecastAlpharetta, GA
September
Weather in September
September in Alpharetta marks the onset of fall, with drastically reduced temperatures from August highs of 88.7°F (31.5°C). A sharp decline in rainfall from August maxima indicates the waning of the damp phase. As the percentage of cloud cover remains the same, the amount of daylight begins to reduce, signaling shorter days ahead. The wind speed begins to pull up again, adding a pleasant edge to the cool weather. The city bids goodbye to summer with a drop in humidity, lowered temperatures and lessned precipitation.Temperature
At the start of September, Alpharetta's average high-temperature reaches a warm 83.5°F (28.6°C), subtly different from the preceding month. Nighttime temperatures in September average to a comfortable 64.8°F (18.2°C) in Alpharetta.Heat index
The heat index value during September is estimated at a hot 89.6°F (32°C). Ongoing activity coupled with exposure often results in weariness and could induce heat cramps.It is essential to grasp that the heat index's numbers are for shade and light wind settings. Exposing to direct sunshine may enhance heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel' or 'feels like', is what the temperature feels like to the human body when the air temperature is combined with the relative humidity. The effect is personal, with varied weather perceptions among individuals due to differences in body mass, stature, and physical activity. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are primarily vital for children. Children often overlook the necessity for resting and fluid replenishment. Thirst is a late sign of dehydration - thus, it is critical to stay hydrated, especially during extended periods of physical activities.
Humidity
In September, the average relative humidity in Alpharetta is 71%.Rainfall
In Alpharetta, during September, the rain falls for 11.5 days and regularly aggregates up to 1.57" (40mm) of precipitation. Throughout the year, there are 158.7 rainfall days, and 26.06" (662mm) of precipitation is accumulated.Snowfall
April through October are months without snowfall in Alpharetta.Daylight
The average length of the day in September in Alpharetta is 12h and 22min.On the first day of September in Alpharetta, sunrise is at 7:11 am and sunset at 8:02 pm. On the last day of the month, sunrise is at 7:31 am and sunset at 7:22 pm EDT.
Sunshine
In September, the average sunshine in Alpharetta is 8.6h.UV index
The average daily maximum UV index in September in Alpharetta is 5. A UV Index estimate of 3 to 5 represents a medium health hazard from unprotected exposure to Sun's UV rays for average individuals.Note: The maximum UV index, 5 during September, leads to the following recommendations:
Prioritize safety - The need to safeguard skin and eyes from harm is emphasized. Given the potency of the midday Sun's UV radiation, one should avoid prolonged exposure. Equip yourself with UVA and UVB-filtering sunglasses on clear, sunny days.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Alpharetta, GA
- Average high temperature in September: 83.5°F
The warmest month (with the highest average high temperature) is July (90°F).
The month with the lowest average high temperature is January (49.1°F).
- Average low temperature in September: 64.8°F
The month with the highest average low temperature is July (70.3°F).
The coldest month (with the lowest average low temperature) is January (33.6°F).
Average pressure in September
Alpharetta, GA
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.99"Hg).
Average wind speed in September
Alpharetta, GA
- Average wind speed in September: 4.8mph
The windiest month (with the highest average wind speed) is January (7.8mph).
The calmest month (with the lowest average wind speed) is August (4.5mph).
Average humidity in September
Alpharetta, GA
- Average humidity in September: 71%
The month with the highest relative humidity is December (78%).
The months with the lowest relative humidity are July and August (69%).
Average rainfall in September
Alpharetta, GA
- Average rainfall in September: 1.57"
The wettest month (with the highest rainfall) is August (3.58").
The driest month (with the least rainfall) is October (1.34").
Average rainfall days in September
Alpharetta, GA
- Average rainfall days in September: 11.5 days
The month with the highest number of rainy days is July (18.8 days).
The month with the least rainy days is October (9 days).
Average snowfall in September
Alpharetta, GA
- Average snowfall in September: 0"
The month with the highest snowfall is January (0.71").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Alpharetta, GA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (1.5 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Alpharetta, GA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).
- Average sunshine in September: 8h and 36min
The month with the most sunshine is July (Average sunshine: 10h and 36min).
The month with the least sunshine is December (Average sunshine: 5h and 6min).
Average sunshine days in September
Alpharetta, GA
- Average sunshine days in September: 16.7 days
The month with the most sunshine days is October (20.5 days).
The month with the least sunshine days is July (10.1 days).
Average UV index in September
Alpharetta, GA
- Average UV index in September: 5
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January and December (UV index 2).
Average cloud cover in September
Alpharetta, GA
- Average cloud cover in September: 31
The months with the most cloud cover are February and December (Cloud cover 46).
The month with the least cloud cover is June (Cloud cover 30).
Average visibility in September
Alpharetta, GA
- 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).
