Decatur Wtp, IL Climate: Temperature & Rain by Month
Average temperature and precipitation from NOAA NCEI 1991–2020 normals →, with a derived climate comfort score
30-year climate normals (1991-2020) from Decatur Wtp's primary NOAA station, DECATUR WTP.
The climate verdict for Decatur Wtp
Decatur Wtp, Illinois has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 53°F. Its climate comfort score of 68/100 (good) lands mid-pack nationally, exceeding 56% of station-mapped location scores.
- 53°F
- annual average temperature (NOAA normal)
- 68/100
- comfort score, above 56% of station-mapped location scores
- 40.4"
- annual precipitation · 14" snow
- 193 days
- growing season, frost-free days
Decatur Wtp: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00112193 · Decatur Wtp, IL 53°F mean · 40.4" precip
TEMP-COOL · RANK-MID · PHOTO-FINISH · PRCP-MID · SWING-WIDE · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 53°F
- RANK-MID #3,636
- PHOTO-FINISH ≈ Lees Summit Ree…
- PRCP-MID 40.4"
- SWING-WIDE 49°F
- COMF-MID 68/100
- LOAD-HEAT 5,443 HDD
- STN-1 USC00112193
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Lees Summit Reed Wildlife Refuge, MO (+ 0 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every IL station list.
- Decatur Wtp (this station) 53°F
- Cold Springfield, IL 53°F
- Hot Vandalia, MO 53°F
- Near Lees Summit Ree…, MO 53°F
- Near Sullivan, IL 53°F
Climate Living Index · Decatur Wtp
Decatur Wtp: 64/100 · grade C
Decatur Wtp publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Decatur Wtp, not an official NOAA rating. Rankings still use Comfort Score 68/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 40.4 in · 5.4 from 35 in | 81/100 · B |
| Normal heat + freeze calendar | 113 calendar days | 69/100 · C |
| Frost-free season | 193 days/year | 59/100 · C |
| Snowfall burden | 13.6 inches/year | 58/100 · C |
| Annual temperature balance | 53.0°F · 14.5° from 67.5°F | 53/100 · D |
Decatur Wtp · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Decatur Wtp is a continental Köppen climate: Dfa
Coldest-month mean 26.9°F and warmest-month mean 75.6°F place this station in continental, no dry season, hot summer climates (Dfa). Class Dfa is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: continental, specifically continental, no dry season, hot summer.
- Köppen code
- Dfa
- Group
- Continental
- Warmest month
- 75.6°F
- Coldest month
- 26.9°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Decatur Wtp sits across the climate record
Three NOAA fields for Decatur Wtp's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 53rd percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 59th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Wider than 76%
- Warmest-to-coldest month gap for Decatur Wtp is large versus 6,861 complete station-years.
How Decatur Wtp compares across U.S. station-mapped locations
Decatur Wtp's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
68 Top 44% score exceeds 56% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). This entry sits in this band.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Decatur Wtp's measured station temperature trend
MethodologyAcross 110 complete annual observations from 1894 to 2024, DECATUR WTP warmed at a fitted rate of 0.09°C per decade. The line shows the fitted change relative to its first year, not raw year-to-year temperatures or a forecast.
- Decatur Wtp primary station fitted change +0.09 °C/decade
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 34°F (1°C) | 20°F (-7°C) | 27°F (-3°C) | 2.4" | 5.9" | 27.1 | 0.0 |
| February | 39°F (4°C) | 24°F (-5°C) | 31°F (0°C) | 2.0" | 2.5" | 22.9 | 0.0 |
| March | 51°F (10°C) | 33°F (0°C) | 42°F (5°C) | 2.6" | 0.9" | 16.1 | 0.0 |
| April | 63°F (17°C) | 43°F (6°C) | 53°F (12°C) | 4.1" | 0.4" | 3.9 | 0.0 |
| May | 74°F (23°C) | 54°F (12°C) | 64°F (18°C) | 5.0" | 0.0" | 0.1 | 0.6 |
| June | 82°F (28°C) | 63°F (17°C) | 73°F (23°C) | 4.7" | 0.0" | 0.0 | 6.2 |
| July | 85°F (29°C) | 67°F (19°C) | 76°F (24°C) | 4.0" | 0.0" | 0.0 | 9.0 |
| August | 84°F (29°C) | 65°F (18°C) | 74°F (23°C) | 3.5" | 0.0" | 0.0 | 6.9 |
| September | 78°F (25°C) | 57°F (14°C) | 67°F (20°C) | 3.1" | 0.0" | 0.1 | 3.3 |
| October | 65°F (19°C) | 46°F (8°C) | 56°F (13°C) | 3.4" | 0.0" | 2.2 | 0.1 |
| November | 50°F (10°C) | 34°F (1°C) | 42°F (6°C) | 3.2" | 0.4" | 13.2 | 0.0 |
| December | 39°F (4°C) | 25°F (-4°C) | 32°F (0°C) | 2.4" | 3.5" | 24.1 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 85°F around July 7, short of 90°F on every date, while 113 dates carry a normal low at or below freezing, the coldest 19°F near January 20.
The freezing stretch
The normal low stays at or below 32°F into March 13, then returns to freezing around November 22, covering 113 dates in all.
Derived from the normal daily minimum. This is a different measure from the 50%-probability frost dates shown elsewhere on this page, which come from NOAA’s frost product.
Where the wet dates fall
The likeliest wet date is May 9, when 43% of years recorded at least a hundredth of an inch. The driest is August 19 at 25%. Summed across the calendar, that is about 116 wet dates a year.
The widest day
September 20 carries the biggest normal gap between afternoon and dawn, 21°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Decatur Wtp.
Where Decatur Wtp Stands Nationally
Among the steadiest day-night climates ranked: even the widest normal daily swing holds to roughly 21°F.
Decatur Wtp earns one nationally notable standing (outer quintile) against 6,860 NOAA 1991–2020 normals stations, middle-of-the-pack metrics stay silent here.
Monthly Precipitation
Average monthly rainfall and snowfall
Snow: 5.9"
9.2 days with precipitation
Snow: 2.5"
8.3 days with precipitation
Snow: 0.9"
9.9 days with precipitation
Snow: 0.4"
11.4 days with precipitation
13.3 days with precipitation
10.5 days with precipitation
9.5 days with precipitation
7.4 days with precipitation
7.8 days with precipitation
9.6 days with precipitation
Snow: 0.4"
9.4 days with precipitation
Snow: 3.5"
9.2 days with precipitation
Decatur Wtp spreads its precipitation across the year
Neither half of the year dominates here: June through August take 30% of the annual total and December through February 17%, with neither reaching the 35% that would mark a distinct wet season. Decatur Wtp has no dry season to plan around, though it does carry a wide 48.7°F gap between its warmest and coldest month.
The gap between the wettest and driest month still matters: May averages 5.0" and February 2.0". The three wettest months together take 34% of the year, against the 25% a perfectly flat distribution would give them.
Shares are computed from this station's own 1991-2020 monthly precipitation normals. "Spread across the year" means neither the June-August nor the December-February share reaches 35%; it describes an average year, not the variability of any single one.
When it rains in Decatur Wtp, it arrives in quantity
40.4" of precipitation falls across only about 116 wet days here, averaging 0.35 inches each. Fewer days carry more water: the year's total is delivered in comparatively heavy events rather than persistent damp.
- Days with measurable precipitation
- about 116 a year, 32% of all days
- Average depth per wet day
- 0.35 inches
- Most wet days
- May, about 13
- Fewest wet days
- August, about 7
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year, and a per-day average is not a forecast of any individual storm.
Winter brings real snow to Decatur Wtp
Decatur Wtp averages 13.6 inches of snowfall a year, with January the snowiest month on the normals, spread across roughly 10 days that record measurable snow. That is depth accumulating on the ground, which is why it can exceed the annual precipitation figure: precipitation counts the liquid the snow melts down to, and fresh snow is mostly air.
- Annual snowfall: 13.6 inches of depth.
- Days recording measurable snow: about 10 a year.
- At a rough ten-to-one melt ratio, snow accounts for on the order of 3% of the year's precipitation.
NOAA 1991-2020 normals. The ten-to-one ratio is a convention, not a measurement: real ratios vary with temperature, so treat the share as an order of magnitude rather than an exact split.
Frost Dates & Growing Season
First Fall Freeze
October 24
50% probability date
Last Spring Freeze
April 14
50% probability date
Growing Season
193 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
5,443
Higher = more heating needed
Cooling Degree Days
1,116
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside IL closest to Decatur Wtp on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (53°F here).
- Centerport, NY 53°F · 0.0°F off
- Emmitsburg, MD 53°F · 0.0°F off
- Glencoe, KY 53°F · 0.0°F off
- Goldfield, NV 53°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (40.4" here), excluding temperature-peer places.
- Covelo, CA 40.4" · 0.0" off
- Brunswick, MO 40.4" · 0.0" off
- Hallettsville, TX 40.4" · 0.0" off
- Painesville, OH 40.5" · 0.0" off
Snow and freeze rhythm
When cold and snow define Decatur Wtp
heating led · moderate · mid swing
Decatur Wtp's energy balance leans toward cold weather: 5,443 annual heating degree days against 1,116 for cooling. Its 48.7°F seasonal range still makes the monthly rows more useful than the annual average alone.
Decatur Wtp's frost-free season lasts about 193 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
-
1. Decatur Wtp coldest normal
January
The monthly mean of 27°F (-3°C) sits near freezing, so cold nights and above-freezing afternoons share the same month.
-
2. Decatur Wtp typical freeze period
January through December
The station reports average freezing days from January through December.
-
3. Decatur Wtp snow peak
January
Decatur Wtp averages 13.6 inches of snow a year, with January the snowiest month on the normals.
Questions about Decatur Wtp's climate
How much snow does Decatur Wtp get? ▼
How cold does Decatur Wtp get in winter? ▼
How much energy does heating and cooling require in Decatur Wtp? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Decatur Wtp's primary station: DECATUR WTP (USC00112193). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Decatur Wtp; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Decatur Wtp comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.