Allegheny County (Pittsburgh)
September
Weather in Allegheny County, Pennsylvania for September 2026
Your guide to Allegheny County weather in September - trends and predictions
So far, September 2026 in Allegheny County is slightly warmer than the historical average by 1.7 °F.
Expect cooler weather in the next days in Allegheny County with the forecast suggesting a temperature of 18.2 °F, lower than the historical average.
In general, the average temperature in Allegheny County at the beginning of September is 27.9 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 18.7 °F by the end of September.
The climate of Allegheny County in September is notably wet, with an average of 15 rainy days, and a total of 138.5 mm of precipitation.
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Temperatures
Rain 🌧️
More
15
Dry days
15
Rainy days
0
Snow days
25°/14°
Temperatures
11 km/h
Avg max wind
68 %
Avg humidity
Allegheny County Weather September
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Temperatures trend during September in Allegheny County
See the weather trend as well as the moving average line
September weather in Allegheny County day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Sunny | 29° /15° | 0 mm | 6 | |
| Sept. 2 | Sunny | 28° /14° | 0 mm | 7 | |
| Sept. 3 | Sunny | 30° /16° | 0.1 mm | 7 | |
| Sept. 4 |  Thundery outbreaks possible | 27° /16° | 15.6 mm | 6 | |
| Sept. 5 |  Partly cloudy | 29° /16° | 0.1 mm | 7 | |
| Sept. 6 | Sunny | 28° /15° | 16.3 mm | 7 | |
| Sept. 7 |  Light rain shower | 24° /13° | 3 mm | 6 | |
| Sept. 8 |  Overcast | 24° /11° | 0 mm | 6 | |
| Sept. 9 | Partly cloudy | 27° /13° | 2.4 mm | 5 | |
| Sept. 10 | Sunny | 27° /14° | 11.7 mm | 5 | |
| Sept. 11 | Overcast | 27° /14° | 0.1 mm | 6 | |
| Sept. 12 |  Mist | 28° /15° | 4.7 mm | 6 | |
| Sept. 13 | Overcast | 26° /15° | 4.4 mm | 5 | |
| Sept. 14 | Sunny | 25° /13° | 0.1 mm | 7 | |
| Sept. 15 | Sunny | 27° /13° | 0 mm | 6 | |
| Sept. 16 | Overcast | 25° /13° | 0.5 mm | 5 | |
| Sept. 17 | Overcast | 22° /15° | 6.1 mm | 4 | |
| Sept. 18 |  Patchy light rain with thunder | 24° /14° | 0.3 mm | 5 | |
| Sept. 19 | Overcast | 25° /15° | 0.1 mm | 6.6 | |
| Sept. 20 | Patchy rain possible | 23° /17° | 3.5 mm | 3 | |
| Sept. 21 | Light rain shower | 16° /13° | 6.7 mm | 0.8 | |
| Sept. 22 | Patchy rain possible | 16° /11° | 1.9 mm | 4 | |
| Sept. 23 | Light rain shower | 14° /11° | 5.9 mm | 3 | |
| Sept. 24 | Light rain shower | 16° /12° | 3.5 mm | 4 | |
| Sept. 25 | Patchy rain possible | 17° /12° | 1.1 mm | 4 | |
| Sept. 26 | Sunny | 20° /10° | 0 mm | 6 | |
| Sept. 27 | Sunny | 19° /11° | 0 mm | 5 | |
| Sept. 28 | Sunny | 20° /11° | 0 mm | 6 | |
| Sept. 29 | Overcast | 20° /11° | 0 mm | 6 | |
| Sept. 30 | Overcast | 19° /14° | 0 mm | 4 | |
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Important Notice
Our weather forecast for Allegheny County in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Allegheny County forecast closer to your planned date for the most up-to-date weather information.
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Allegheny County in September - FAQ
What are the expected maximum and minimum temperatures in Allegheny County during September?
Enjoy moderate daytime temperatures of up to 25° and cooler nights around 14°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Allegheny County during September?
Significant rainfall exceeding 138.5 mm is expected in Allegheny County during September, occurring over more than 15 days. Preparing for wet conditions is recommended in your planning.
What are the typical wind conditions in Allegheny County during September?
The average wind speed in Allegheny County during September is 11 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Allegheny County
Explore the daily rainfall trends and prepare for Allegheny Countys September weather 💧
Typically, Allegheny County has 15 rainy days in September with a total of 138.5 mm of rainfall.
UV exposure in Allegheny County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Where is Allegheny County?Get accurate weather forecasts for Allegheny County, located at latitude 40.441 and longitude -79.996. Stay updated with localized weather information tailored for Allegheny County.
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