September
September · June · May
88climate match
United States · 1991–2020
Best time to visit
Gilliam.
September leads for comfortable weather in Gilliam: typically 25.9°C by day, 12°C at night, with 16 mm of rain. Based on measured 1991–2020 NOAA station history.
Best comfortSeptember
Typical high25.9°C
Typical low12°C
Rain in September16 mm
August
August · July · June
79climate match
May
May · October · September
85climate match
The weakest month is January, scoring 5 against September’s 88 — days reach only 5.5°C, 18° below the 24°C the score treats as ideal.
Month by month
The whole year,
without the guesswork.
The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.
Jan
55.5° / -0.8°
Feb
168.1° / 0.4°
Mar
3513.2° / 3°
Apr
5417.1° / 5.6°
May
7822.1° / 9.5°
Jun
8626.4° / 12.8°
Jul
6932.4° / 16.7°
Aug
7231.6° / 16.5°
Sep
8825.9° / 12°
Oct
6017.7° / 6.5°
Nov
199.5° / 1.8°
Dec
55° / -1.2°
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | 5.5°C | -0.8°C | 49 mm | 9.2 | 9 h | 5 | Strong coverage |
| February | 8.1°C | 0.4°C | 41 mm | 8 | 10 h 16 | 16 | Strong coverage |
| March | 13.2°C | 3°C | 53 mm | 9.3 | 11 h 45 | 35 | Strong coverage |
| April | 17.1°C | 5.6°C | 48 mm | 8.1 | 13 h 29 | 54 | Strong coverage |
| May | 22.1°C | 9.5°C | 52 mm | 7.1 | 14 h 56 | 78 | Strong coverage |
| June | 26.4°C | 12.8°C | 32 mm | 5.2 | 15 h 45 | 86 | Strong coverage |
| July | 32.4°C | 16.7°C | 12 mm | 1.7 | 15 h 25 | 69 | Strong coverage |
| August | 31.6°C | 16.5°C | 10 mm | 1.4 | 14 h 09 | 72 | Strong coverage |
| September | 25.9°C | 12°C | 16 mm | 2.4 | 12 h 29 | 88 | Strong coverage |
| October | 17.7°C | 6.5°C | 40 mm | 6.6 | 10 h 50 | 60 | Strong coverage |
| November | 9.5°C | 1.8°C | 56 mm | 10.2 | 9 h 22 | 19 | Strong coverage |
| December | 5°C | -1.2°C | 55 mm | 10.4 | 8 h 39 | 5 | Strong coverage |
What has changed
Gilliam runs +0.4°C
on the 1961–1990 baseline.
Each bar compares the 2011–2025 daytime average for that month against the same month in 1961–1990, measured at the same station. Months where the older record is too thin to compare are left blank.
Jan
+1.2
Feb
-0.7
Mar
+0.3
Apr
-0.1
May
+0.7
Jun
+0.1
Jul
+1.1
Aug
+1.0
Sep
+0.8
Oct
-0.3
Nov
-0.1
Dec
+0.9
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 21.1°C20 Jan 1968 | -27.8°C27 Jan 1957 | 33 mm1 Jan 1994 | 150 mm1970 · driest 9 mm in 2005 | 75 |
| February | 23.9°C20 Feb 1995 | -26.7°C1 Feb 1950 | 41 mm23 Feb 2002 | 105 mm1986 · driest 9 mm in 2005 | 75 |
| March | 26.1°C26 Mar 2025 | -15.6°C1 Mar 1993 | 35 mm4 Mar 1983 | 110 mm1983 · driest 11 mm in 1965 | 74 |
| April | 35.6°C24 Apr 1977 | -6.7°C19 Apr 1966 | 41 mm27 Apr 1990 | 102 mm1978 · driest 4 mm in 1956 | 74 |
| May | 37.8°C28 May 1983 | -3.3°C1 May 1954 | 43 mm26 May 1971 | 168 mm1991 · driest 7 mm in 1992 | 74 |
| June | 46.7°C29 Jun 2021 | 2.2°C1 Jun 1966 | 38 mm7 Jun 1950 | 89 mm2012 · driest 0 mm in 2025 | 74 |
| July | 45.6°C10 Jul 1975 | 4.4°C7 Jul 1971 | 93 mm23 Jul 1992 | 120 mm1992 · driest 0 mm in 2017 | 74 |
| August | 45.6°C4 Aug 1961 | 5.6°C24 Aug 1992 | 58 mm22 Aug 1992 | 79 mm1977 · driest 0 mm in 1967 | 73 |
| September | 40.0°C2 Sep 1950 | 0.0°C29 Sep 1985 | 43 mm8 Sep 2003 | 73 mm1959 · driest 0 mm in 2018 | 73 |
| October | 31.7°C3 Oct 1958 | -9.4°C31 Oct 2002 | 40 mm31 Oct 1994 | 116 mm2016 · driest 0 mm in 1987 | 73 |
| November | 27.2°C12 Nov 1999 | -23.9°C23 Nov 1985 | 38 mm4 Nov 1994 | 130 mm1973 · driest 13 mm in 1952 | 74 |
| December | 21.7°C10 Dec 2014 | -31.1°C30 Dec 1968 | 35 mm5 Dec 1971 | 137 mm1973 · driest 13 mm in 1965 | 74 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 17 | 1 | 2 |
| February | 0 | 0 | 13 | <1 | 2 |
| March | <1 | 0 | 6 | 1 | <1 |
| April | 2 | 0 | 1 | 1 | 0 |
| May | 10 | 3 | <1 | 2 | 0 |
| June | 18 | 8 | 0 | <1 | 0 |
| July | 29 | 22 | 0 | <1 | 0 |
| August | 29 | 21 | 0 | <1 | 0 |
| September | 18 | 7 | 0 | <1 | 0 |
| October | 3 | <1 | 2 | 1 | <1 |
| November | 0 | 0 | 10 | 1 | <1 |
| December | 0 | 0 | 20 | 1 | 2 |
| Month | Warm & dry days | Wet days | Washouts | Week with 3+ wet days | Daytime mean has ranged |
|---|---|---|---|---|---|
| January | <1% | 31% | 4% | 39% | -1.0–8.6°C |
| February | <1% | 29% | 3% | 36% | 5.0–10.7°C |
| March | 5% | 29% | 4% | 34% | 10.5–14.5°C |
| April | 24% | 25% | 4% | 29% | 15.0–19.7°C |
| May | 55% | 20% | 4% | 20% | 19.2–24.0°C |
| June | 80% | 16% | 3% | 12% | 24.1–29.4°C |
| July | 94% | 6% | <1% | 3% | 29.8–34.4°C |
| August | 93% | 7% | 1% | 4% | 28.2–33.5°C |
| September | 82% | 11% | 2% | 9% | 23.0–28.4°C |
| October | 31% | 20% | 4% | 23% | 16.0–20.2°C |
| November | 2% | 33% | 5% | 46% | 6.6–11.9°C |
| December | 0% | 34% | 5% | 44% | 1.7–7.8°C |
A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.
The evidence behind this page
Nearby, measured,
and named.
- Place identity
- GeoNames 5555205
- NOAA station
- USW00024160 · WALLA WALLA RGNL AP
- Station distance
- 9 km from the place centre
- Climate period
- 1991–2020
- Minimum month coverage
- 26 usable years
- Daylight
- Calculated from latitude 46.13°, mid-month, sunrise to sunset including refraction. Not a station measurement.
- Important limit
- Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.