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September Weather in Alpharetta, United States

Last updated: June 24, 2025

In September, the average temperature in Alpharetta, United States hovers around 23°C (74°F), making it a pleasant time to visit. Expect temperatures to range from a minimum of 10°C (50°F) to a maximum of 35°C (96°F). However, be prepared for some rain, as the area receives about 115 mm (4.5 in) of precipitation over 10 days. With an average humidity of 82%, it's advisable to stay hydrated and cool during your adventures!

September Temperature in Alpharetta

In September in Alpharetta, the average temperature is 23°C (74°F). Maximum temperatures can reach up to 35°C (96°F), while minimum temperatures can drop as low as 10°C (50°F). This makes Alpharetta a pleasant destination for travelers seeking warm days and cool nights.

September Weather in Alpharetta: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Alpharetta, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Alpharetta, September typically has an average temperature of 23°C (74°F), with highs reaching up to 35°C (96°F) and lows dropping to around 10°C (50°F).
JanFebMarAprMayJunJulAugSepOctNovDec455055617075797874655248
Data source: Temperature data for Alpharetta generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Alpharetta

In Alpharetta in September, the precipitation amount is 115 mm (4.5 in) over a span of 10 days.

September Precipitation Trends in Alpharetta

The chart displays monthly precipitation patterns in Alpharetta, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Alpharetta, September typically receives around 115 mm (4.5 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec11216014212911613411815611514083141
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Alpharetta

In Alpharetta in September, humidity is 82%. With an average temperature of 23°C (74°F), this humidity feels like you are walking through a warm, damp blanket, making travel a bit uncomfortable and sticky as you navigate the air thick with moisture.

September Average Humidity in Alpharetta

This chart illustrates the average monthly humidity levels in Alpharetta, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Alpharetta is approximately 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%83%81%81%81%83%81%82%78%86%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Alpharetta

In Alpharetta in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Alpharetta.

Maximum UV Index Levels in Alpharetta for September

The chart shows the monthly maximum UV Index (UVI) for Alpharetta in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Alpharetta typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec47810111111109864
Data source: Alpharetta September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Alpharetta Compares to Other Months

Weather in Alpharetta varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Alpharetta, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Alpharetta, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather7°C (45°F)112 mm (4.4 inches)86%moderate
February Weather10°C (50°F)160 mm (6.3 inches)84%high
March Weather13°C (56°F)142 mm (5.6 inches)83%very high
April Weather16°C (62°F)129 mm (5.1 inches)81%very high
May Weather21°C (71°F)116 mm (4.6 inches)81%extreme
June Weather24°C (76°F)134 mm (5.3 inches)81%extreme
July Weather26°C (79°F)118 mm (4.7 inches)83%extreme
August Weather25°C (78°F)156 mm (6.1 inches)81%very high
September Weather23°C (74°F)115 mm (4.5 inches)82%very high
October Weather18°C (65°F)140 mm (5.5 inches)78%very high
November Weather11°C (52°F)83 mm (3.3 inches)86%high
December Weather9°C (48°F)141 mm (5.5 inches)89%moderate

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