Williamsport weather in September: Williamsport, Pennsylvania: normal highs, lows, rain and records for September
Williamsport in September has a normal high of 75°F and a normal low of 54°F, a daily mean of 65°F, falling from 80°F on the 1st to 70°F by the 30th. Measurable precipitation falls on 10 days in a normal September, 4.76 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 24°C and low of 12°C, 121 mm of precipitation in September.
- NOAA stationWilliamsport Regional Airport
- Station IDUSW00014778
- Location41.24°N 76.92°W
- Elevation520 ft (159 m)
- Population27,628
- Jan 35° 20°
- Feb 39° 22°
- Mar 48° 29°
- Apr 62° 39°
- May 72° 49°
- Jun 81° 58°
- Jul 85° 63°
- Aug 83° 61°
- Sep 75° 54°
- Oct 63° 43°
- Nov 51° 33°
- Dec 40° 26°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Williamsport in September?
The normal high is 75°F and the normal low 54°F, for a daily mean of 64.7°F. September is 7.3°F cooler than August and 11.7°F warmer than October. September is the 4th warmest month of the year in Williamsport and the wettest. Across the month the normal high falls 10°F, from 80°F on September 1 to 70°F on September 30. From one year to the next September's mean temperature typically moves about 2.2°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 63°F and 67°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 35%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 80°F | 59°F | 32% | 20% |
| September 8 | 78°F | 57°F | 32% | 20% |
| September 15 | 76°F | 55°F | 33% | 20% |
| September 22 | 73°F | 52°F | 34% | 21% |
| September 30 | 70°F | 49°F | 35% | 21% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 80°F | 59°F | 32% | 20% | 13 h 10 min |
| September 2 | 80°F | 58°F | 32% | 20% | 13 h 10 min |
| September 3 | 80°F | 58°F | 32% | 20% | 13 h |
| September 4 | 79°F | 58°F | 32% | 20% | 13 h |
| September 5 | 79°F | 58°F | 32% | 20% | 13 h |
| September 6 | 79°F | 57°F | 32% | 20% | 13 h |
| September 7 | 78°F | 57°F | 32% | 20% | 12 h 50 min |
| September 8 | 78°F | 57°F | 32% | 20% | 12 h 50 min |
| September 9 | 78°F | 56°F | 32% | 20% | 12 h 50 min |
| September 10 | 77°F | 56°F | 32% | 20% | 12 h 50 min |
| September 11 | 77°F | 56°F | 32% | 20% | 12 h 40 min |
| September 12 | 77°F | 56°F | 32% | 20% | 12 h 40 min |
| September 13 | 76°F | 55°F | 33% | 20% | 12 h 40 min |
| September 14 | 76°F | 55°F | 33% | 20% | 12 h 40 min |
| September 15 | 76°F | 55°F | 33% | 20% | 12 h 30 min |
| September 16 | 75°F | 54°F | 33% | 20% | 12 h 30 min |
| September 17 | 75°F | 54°F | 33% | 20% | 12 h 30 min |
| September 18 | 75°F | 53°F | 33% | 21% | 12 h 20 min |
| September 19 | 74°F | 53°F | 33% | 21% | 12 h 20 min |
| September 20 | 74°F | 53°F | 33% | 21% | 12 h 20 min |
| September 21 | 73°F | 52°F | 34% | 21% | 12 h 20 min |
| September 22 | 73°F | 52°F | 34% | 21% | 12 h 10 min |
| September 23 | 73°F | 52°F | 34% | 21% | 12 h 10 min |
| September 24 | 72°F | 51°F | 34% | 21% | 12 h 10 min |
| September 25 | 72°F | 51°F | 34% | 21% | 12 h 10 min |
| September 26 | 71°F | 50°F | 34% | 21% | 12 h |
| September 27 | 71°F | 50°F | 35% | 21% | 12 h |
| September 28 | 70°F | 50°F | 35% | 21% | 12 h |
| September 29 | 70°F | 49°F | 35% | 21% | 11 h 50 min |
| September 30 | 70°F | 49°F | 35% | 21% | 11 h 50 min |
- Normal high
- 75°FSeptember average
- Normal low
- 54°FSeptember average
- Precipitation
- 4.76 inmonth total
- Days with precipitation
- 100.01 inch or more
- Days at 90°F or more
- 1
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 23
- Days at 80°F or more
- 9
- Sunshine
- 72%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00014778; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Williamsport in September?
On a given September day the chance of 0.01 inch or more is 33% on average, highest around September 29 (35%). In all, 4.76 in falls on 10 days of a normal September, 1 of them with an inch or more.
In a normal September in Williamsport, 1 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014778.
How humid and windy is Williamsport in September?
At 3 p.m. the normal temperature is 68°F with 53% relative humidity and a dew point of 50°F; at 6 a.m. it is 52°F with 90% humidity. The wind averages 5.0 mph, most often from the west-southwest in the afternoon.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 52°F | 49°F | 90% | 3.8 mph | – |
| 9 a.m. | 56°F | 50°F | 81% | 5.5 mph | – |
| noon | 65°F | 51°F | 60% | 7.3 mph | 45% |
| 3 p.m. | 68°F | 50°F | 53% | 7.7 mph | 47% |
| 6 p.m. | 62°F | 52°F | 69% | 4.7 mph | 59% |
| 9 p.m. | 57°F | 51°F | 82% | 3.7 mph | 64% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014778. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Williamsport?
The warmest September temperature on Williamsport's official record (since 1895) is 102°F, on September 3, 1953; the coldest is 28°F, on September 28, 1947. The wettest September brought 15.97 in (2011).
The September mean against the 1991-2020 normal of 64.7°F: 2021 66.5°F (+1.8), 2022 65.3°F (+0.6), 2023 66.8°F (+2.1), 2024 66.1°F (+1.4), 2025 67.1°F (+2.4), 2026 66.9°F (+2.2). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 66.5°F | +1.8°F | 8.51 in |
| 2022 | 65.3°F | +0.6°F | 4.64 in |
| 2023 | 66.8°F | +2.1°F | 2.97 in |
| 2024 | 66.1°F | +1.4°F | 1.11 in |
| 2025 | 67.1°F | +2.4°F | 1.38 in |
| 2026 | 66.9°F | +2.2°F | 6.84 in |
Source: records: ACIS, NWS threaded record IPTthr; recent months: ACIS, station USW00014778. Records and recent months use complete months only.
How does September in Williamsport compare across Pennsylvania?
Across the 108 places PlainClimate covers in Pennsylvania, September normal highs run from 68°F in Laporte to 80°F in Marcus Hook; Williamsport's is 75°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- Williamsport in August83°F by day, 61°F at night
- Williamsport in October63°F by day, 43°F at night
- Williamsport through the yearEvery month, frost dates, records and recent years
- Pennsylvania in SeptemberThe statewide normal and the warmest and coolest places
- Marcus Hook: Pennsylvania's warmest Septembernormal high 80°F