September
September · June · August
84climate match
United States · 1991–2020
Best time to visit
Ajax.
September leads for comfortable weather in Ajax: typically 24.8°C by day, 8.1°C at night, with 31 mm of rain. Based on measured 1991–2020 NOAA station history.
Best comfortSeptember
Typical high24.8°C
Typical low8.1°C
Rain in September31 mm
August
August · July · September
73climate match
September
September · May · October
80climate match
The weakest month is January, scoring 5 against September’s 84 — days reach only 2.5°C, 21° below the 24°C the score treats as ideal, and nights drop to -10.7°C.
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
52.5° / -10.7°
Feb
53.7° / -9.9°
Mar
149.3° / -5.1°
Apr
3314° / -0.4°
May
5519.4° / 5.5°
Jun
7625.6° / 10.9°
Jul
7130.5° / 14.7°
Aug
7530° / 13.6°
Sep
8424.8° / 8.1°
Oct
4716.1° / 1°
Nov
138.8° / -5.5°
Dec
53.2° / -10°
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | 2.5°C | -10.7°C | 8 mm | 2.3 | 9 h 14 | 5 | Strong coverage |
| February | 3.7°C | -9.9°C | 13 mm | 3.1 | 10 h 24 | 5 | Strong coverage |
| March | 9.3°C | -5.1°C | 22 mm | 4.2 | 11 h 47 | 14 | Strong coverage |
| April | 14°C | -0.4°C | 53 mm | 7.5 | 13 h 22 | 33 | Strong coverage |
| May | 19.4°C | 5.5°C | 88 mm | 9.5 | 14 h 43 | 55 | Strong coverage |
| June | 25.6°C | 10.9°C | 73 mm | 9.3 | 15 h 27 | 76 | Strong coverage |
| July | 30.5°C | 14.7°C | 58 mm | 7.1 | 15 h 09 | 71 | Strong coverage |
| August | 30°C | 13.6°C | 40 mm | 5.2 | 14 h | 75 | Strong coverage |
| September | 24.8°C | 8.1°C | 31 mm | 4.4 | 12 h 27 | 84 | Strong coverage |
| October | 16.1°C | 1°C | 33 mm | 5 | 10 h 55 | 47 | Strong coverage |
| November | 8.8°C | -5.5°C | 11 mm | 2.9 | 9 h 35 | 13 | Strong coverage |
| December | 3.2°C | -10°C | 9 mm | 2.8 | 8 h 55 | 5 | Strong coverage |
What has changed
Ajax runs +0.8°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
+2.1
Feb
-1.0
Mar
+2.0
Apr
-0.6
May
-0.6
Jun
+1.1
Jul
+0.7
Aug
+0.1
Sep
+2.3
Oct
-0.5
Nov
+1.6
Dec
+1.8
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 24.4°C12 Jan 1987 | -32.8°C4 Jan 1950 | 17 mm30 Jan 1971 | 43 mm1949 · driest 0 mm in 1952 | 78 |
| February | 23.9°C27 Feb 1988 | -35.0°C2 Feb 1996 | 22 mm9 Feb 1953 | 63 mm1953 · driest 1 mm in 1999 | 78 |
| March | 30.6°C21 Mar 2026 | -29.4°C8 Mar 1996 | 35 mm16 Mar 1963 | 69 mm1973 · driest 1 mm in 2012 | 78 |
| April | 33.9°C22 Apr 1989 | -18.2°C3 Apr 2020 | 81 mm5 Apr 1997 | 131 mm1967 · driest 1 mm in 1987 | 78 |
| May | 36.7°C27 May 1969 | -7.8°C1 May 1950 | 82 mm14 May 1965 | 208 mm1996 · driest 8 mm in 1966 | 79 |
| June | 42.8°C29 Jun 2002 | -0.6°C1 Jun 1951 | 96 mm15 Jun 1963 | 181 mm2015 · driest 11 mm in 2002 | 79 |
| July | 44.4°C25 Jul 2026 | 3.9°C13 Jul 1987 | 63 mm15 Jul 2015 | 162 mm2019 · driest 10 mm in 1988 | 79 |
| August | 41.7°C13 Aug 2007 | 2.8°C31 Aug 2020 | 66 mm4 Aug 1982 | 123 mm1982 · driest 7 mm in 1958 | 78 |
| September | 40.0°C5 Sep 2020 | -7.8°C24 Sep 1985 | 54 mm13 Sep 1966 | 81 mm2014 · driest 1 mm in 1975 | 78 |
| October | 35.6°C3 Oct 2025 | -21.6°C26 Oct 2020 | 63 mm9 Oct 1982 | 143 mm1998 · driest 0 mm in 1960 | 78 |
| November | 28.3°C7 Nov 1999 | -28.3°C14 Nov 1959 | 17 mm19 Nov 1977 | 56 mm1985 · driest 0 mm in 2004 | 78 |
| December | 23.9°C4 Dec 1965 | -34.4°C30 Dec 1990 | 26 mm31 Dec 1975 | 42 mm1975 · driest 0 mm in 2001 | 78 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 30 | 0 | 6 |
| February | 0 | 0 | 27 | <1 | 7 |
| March | <1 | 0 | 26 | <1 | 4 |
| April | 3 | <1 | 16 | 2 | 4 |
| May | 6 | 1 | 4 | 3 | <1 |
| June | 17 | 7 | 0 | 2 | 0 |
| July | 27 | 18 | 0 | 2 | 0 |
| August | 27 | 17 | 0 | 1 | 0 |
| September | 16 | 7 | 1 | <1 | <1 |
| October | 4 | 1 | 13 | 1 | 1 |
| November | <1 | 0 | 26 | <1 | 4 |
| December | 0 | 0 | 30 | <1 | 6 |
| Month | Warm & dry days | Wet days | Washouts | Week with 3+ wet days | Daytime mean has ranged |
|---|---|---|---|---|---|
| January | <1% | 9% | <1% | 4% | -3.5–6.2°C |
| February | 2% | 12% | <1% | 9% | -2.2–8.6°C |
| March | 9% | 16% | 2% | 13% | 3.2–12.6°C |
| April | 22% | 23% | 5% | 24% | 10.4–17.8°C |
| May | 42% | 29% | 8% | 37% | 17.0–22.6°C |
| June | 65% | 29% | 8% | 34% | 22.9–29.4°C |
| July | 78% | 21% | 6% | 20% | 27.8–34.1°C |
| August | 82% | 17% | 4% | 13% | 27.6–32.3°C |
| September | 69% | 15% | 3% | 11% | 21.5–27.6°C |
| October | 36% | 13% | 3% | 8% | 14.0–19.8°C |
| November | 8% | 10% | <1% | 6% | 4.6–12.9°C |
| December | 1% | 10% | <1% | 4% | -1.5–7.6°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 5762320
- NOAA station
- USW00024090 · RAPID CITY RGNL AP
- Station distance
- 19.4 km from the place centre
- Climate period
- 1991–2020
- Minimum month coverage
- 30 usable years
- Daylight
- Calculated from latitude 43.90°, 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.