Lewiston weather in September: Lewiston, Idaho: normal highs, lows, rain and records for September
Lewiston in September has a normal high of 80°F and a normal low of 52°F, a daily mean of 66°F, falling from 85°F on the 1st to 73°F by the 30th. Measurable precipitation falls on 5 days in a normal September, 0.60 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 26°C and low of 11°C, 15 mm of precipitation in September.
- NOAA stationLewiston Airport
- Station IDUSW00024149
- Location46.37°N 117.02°W
- Elevation1,436 ft (438 m)
- Population34,693
- Jan 42° 30°
- Feb 47° 32°
- Mar 55° 36°
- Apr 62° 41°
- May 72° 48°
- Jun 79° 54°
- Jul 91° 61°
- Aug 90° 60°
- Sep 80° 52°
- Oct 63° 42°
- Nov 49° 35°
- Dec 41° 30°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Lewiston in September?
The normal high is 80°F and the normal low 52°F, for a daily mean of 65.9°F. September is 9.3°F cooler than August and 13.4°F warmer than October. September is the 4th warmest month of the year in Lewiston and the 10th wettest. Across the month the normal high falls 12°F, from 85°F on September 1 to 73°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 64°F and 68°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 21%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 85°F | 57°F | 13% | 5% |
| September 8 | 83°F | 55°F | 14% | 6% |
| September 15 | 80°F | 53°F | 16% | 7% |
| September 22 | 77°F | 50°F | 18% | 7% |
| September 30 | 73°F | 48°F | 21% | 8% |
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 | 85°F | 57°F | 13% | 5% | 13 h 20 min |
| September 2 | 85°F | 56°F | 13% | 5% | 13 h 20 min |
| September 3 | 85°F | 56°F | 13% | 5% | 13 h 20 min |
| September 4 | 84°F | 56°F | 13% | 5% | 13 h 10 min |
| September 5 | 84°F | 56°F | 13% | 5% | 13 h 10 min |
| September 6 | 84°F | 55°F | 14% | 6% | 13 h 10 min |
| September 7 | 83°F | 55°F | 14% | 6% | 13 h |
| September 8 | 83°F | 55°F | 14% | 6% | 13 h |
| September 9 | 83°F | 54°F | 14% | 6% | 13 h |
| September 10 | 82°F | 54°F | 15% | 6% | 12 h 50 min |
| September 11 | 82°F | 54°F | 15% | 6% | 12 h 50 min |
| September 12 | 81°F | 54°F | 15% | 6% | 12 h 50 min |
| September 13 | 81°F | 53°F | 15% | 6% | 12 h 40 min |
| September 14 | 81°F | 53°F | 16% | 6% | 12 h 40 min |
| September 15 | 80°F | 53°F | 16% | 7% | 12 h 40 min |
| September 16 | 80°F | 52°F | 16% | 7% | 12 h 30 min |
| September 17 | 79°F | 52°F | 17% | 7% | 12 h 30 min |
| September 18 | 79°F | 52°F | 17% | 7% | 12 h 30 min |
| September 19 | 78°F | 51°F | 17% | 7% | 12 h 20 min |
| September 20 | 78°F | 51°F | 18% | 7% | 12 h 20 min |
| September 21 | 77°F | 51°F | 18% | 7% | 12 h 20 min |
| September 22 | 77°F | 50°F | 18% | 7% | 12 h 20 min |
| September 23 | 76°F | 50°F | 19% | 7% | 12 h 10 min |
| September 24 | 76°F | 50°F | 19% | 7% | 12 h 10 min |
| September 25 | 75°F | 49°F | 19% | 8% | 12 h 10 min |
| September 26 | 75°F | 49°F | 20% | 8% | 12 h |
| September 27 | 74°F | 49°F | 20% | 8% | 12 h |
| September 28 | 74°F | 48°F | 20% | 8% | 12 h |
| September 29 | 73°F | 48°F | 21% | 8% | 11 h 50 min |
| September 30 | 73°F | 48°F | 21% | 8% | 11 h 50 min |
- Normal high
- 80°FSeptember average
- Normal low
- 52°FSeptember average
- Precipitation
- 0.60 inmonth total
- Days with precipitation
- 50.01 inch or more
- Days at 90°F or more
- 4
- Daylight
- 13 h 20 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 25
- Days at 80°F or more
- 15
- Sunshine
- 83%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024149; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Lewiston in September?
On a given September day the chance of 0.01 inch or more is 16% on average, highest around September 30 (21%). In all, 0.60 in falls on 5 days of a normal September.
In a normal September in Lewiston, 4 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024149.
How humid and windy is Lewiston in September?
At 3 p.m. the normal temperature is 71°F with 31% relative humidity and a dew point of 39°F; at 6 a.m. it is 49°F with 69% humidity. The wind averages 4.6 mph, most often from the northwest in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 49°F | 39°F | 69% | 3.6 mph | 78% |
| 9 a.m. | 57°F | 41°F | 56% | 4.4 mph | 76% |
| noon | 67°F | 41°F | 39% | 5.2 mph | 78% |
| 3 p.m. | 71°F | 39°F | 31% | 6.3 mph | 75% |
| 6 p.m. | 66°F | 39°F | 37% | 4.9 mph | 81% |
| 9 p.m. | 59°F | 39°F | 47% | 5.0 mph | 81% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024149. 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 Lewiston?
The warmest September temperature on Lewiston's official record (since 1881) is 108°F, on September 6, 1944; the coldest is 27°F, on September 24, 1926. The wettest September brought 4.37 in (1940).
The September mean against the 1991-2020 normal of 65.9°F: 2021 66.7°F (+0.8), 2022 68.9°F (+3.0), 2023 66.4°F (+0.5), 2024 70.0°F (+4.1), 2025 71.3°F (+5.4), 2026 63.3°F (−2.7). 5 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 66.7°F | +0.8°F | 0.69 in |
| 2022 | 68.9°F | +3.0°F | 1.38 in |
| 2023 | 66.4°F | +0.5°F | 1.04 in |
| 2024 | 70.0°F | +4.1°F | 0.82 in |
| 2025 | 71.3°F | +5.4°F | 1.24 in |
| 2026 | 63.3°F | −2.7°F | 1.63 in |
Source: records: ACIS, NWS threaded record LWSthr; recent months: ACIS, station USW00024149. Records and recent months use complete months only.
How does September in Lewiston compare across Idaho?
Across the 85 places PlainClimate covers in Idaho, September normal highs run from 59°F in Mullan to 86°F in Glenns Ferry; Lewiston's is 80°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.