Petersburg, IL Climate: Temperature & Rain by Month
Temperature and precipitation from NOAA NCEI 1991–2020 normals →, plus PlainClimate's derived comfort score
30-year climate normals (1991-2020) from Petersburg's primary NOAA station, PETERSBURG 1E.
The climate verdict for Petersburg
Petersburg, Illinois has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 52°F. Its climate comfort score of 68/100 (good) lands mid-pack nationally, exceeding 56% of station-mapped location scores.
- 52°F
- average temperature, NOAA 1991-2020 normal
- 68/100
- comfort score, above 56% of station-mapped location scores
- 37.6"
- annual precipitation · 15" snow
- 191 days
- frost-free growing season
Petersburg: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00116765 · Petersburg, IL 52°F mean · 37.6" precip
TEMP-COOL · RANK-MID · PHOTO-FINISH · PRCP-MID · SWING-WIDE · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 52°F
- RANK-MID #3,431
- PHOTO-FINISH ≈ Leoti
- PRCP-MID 37.6"
- SWING-WIDE 50°F
- COMF-MID 68/100
- LOAD-HEAT 5,644 HDD
- STN-1 USC00116765
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Leoti, KS (+ 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.
- Petersburg (this station) 52°F
- Cold Hoopeston, IL 52°F
- Hot Tuscola, IL 52°F
- Near Leoti, KS 52°F
- Near Fruita, CO 52°F
Climate Living Index · Petersburg
Petersburg: 62/100 · grade C
Petersburg publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Petersburg, not an official NOAA rating. Rankings still use Comfort Score 68/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 37.6 in · 2.6 from 35 in | 90/100 · A |
| Normal heat + freeze calendar | 126 calendar days | 61/100 · C |
| Frost-free season | 191 days/year | 58/100 · C |
| Snowfall burden | 15.2 inches/year | 56/100 · C |
| Annual temperature balance | 52.3°F · 15.2° from 67.5°F | 50/100 · D |
Petersburg · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Petersburg is a continental Köppen climate: Dfa
Coldest-month mean 25.9°F and warmest-month mean 75.5°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
- 75.5°F
- Coldest month
- 25.9°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 Petersburg sits across the climate record
Three NOAA fields for Petersburg's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 50th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 53rd percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Wider than 80%
- Warmest-to-coldest month gap for Petersburg is large versus 6,861 complete station-years.
How Petersburg compares across U.S. station-mapped locations
Petersburg'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
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) | 17°F (-8°C) | 26°F (-3°C) | 2.0" | 5.4" | 27.2 | 0.0 |
| February | 39°F (4°C) | 21°F (-6°C) | 30°F (-1°C) | 1.8" | 2.7" | 23.8 | 0.0 |
| March | 51°F (10°C) | 30°F (-1°C) | 41°F (5°C) | 2.5" | 1.4" | 17.8 | 0.0 |
| April | 64°F (18°C) | 41°F (5°C) | 53°F (11°C) | 4.1" | 0.5" | 6.8 | 0.0 |
| May | 74°F (23°C) | 53°F (12°C) | 64°F (18°C) | 4.6" | 0.0" | 0.2 | 0.5 |
| June | 82°F (28°C) | 62°F (17°C) | 72°F (22°C) | 4.1" | 0.0" | 0.0 | 5.0 |
| July | 86°F (30°C) | 65°F (19°C) | 76°F (24°C) | 3.9" | 0.0" | 0.0 | 7.5 |
| August | 85°F (29°C) | 63°F (17°C) | 74°F (23°C) | 3.7" | 0.0" | 0.0 | 2.2 |
| September | 79°F (26°C) | 55°F (13°C) | 67°F (19°C) | 3.1" | 0.0" | 0.0 | 4.1 |
| October | 66°F (19°C) | 43°F (6°C) | 55°F (13°C) | 3.2" | 0.0" | 3.5 | 0.0 |
| November | 52°F (11°C) | 32°F (0°C) | 42°F (5°C) | 2.8" | 1.2" | 17.1 | 0.0 |
| December | 39°F (4°C) | 23°F (-5°C) | 31°F (-1°C) | 1.9" | 4.0" | 24.3 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 86°F around July 24, short of 90°F on every date, while 126 dates carry a normal low at or below freezing, the coldest 17°F near January 15.
The freezing stretch
The normal low stays at or below 32°F into March 20, then returns to freezing around November 16, covering 126 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 1, when 39% of years recorded at least a hundredth of an inch. The driest is September 17 at 24%. Summed across the calendar, that is about 105 wet dates a year.
The widest day
September 26 carries the biggest normal gap between afternoon and dawn, 25°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Petersburg.
Monthly Precipitation
Average monthly rainfall and snowfall
Snow: 5.4"
8.7 days with precipitation
Snow: 2.7"
7.4 days with precipitation
Snow: 1.4"
9.8 days with precipitation
Snow: 0.5"
10.7 days with precipitation
11.4 days with precipitation
9.0 days with precipitation
8.3 days with precipitation
7.6 days with precipitation
7.0 days with precipitation
8.5 days with precipitation
Snow: 1.2"
8.0 days with precipitation
Snow: 4.0"
7.8 days with precipitation
Petersburg spreads its precipitation across the year
Neither half of the year dominates here: June through August take 31% of the annual total and December through February 15%, with neither reaching the 35% that would mark a distinct wet season. Petersburg has no dry season to plan around, though it does carry a wide 49.6°F gap between its warmest and coldest month.
The gap between the wettest and driest month still matters: May averages 4.6" and February 1.8". 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 Petersburg, it arrives in quantity
37.6" of precipitation falls across only about 104 wet days here, averaging 0.36 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 104 a year, 29% of all days
- Average depth per wet day
- 0.36 inches
- Most wet days
- May, about 11
- Fewest wet days
- September, 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 Petersburg
Petersburg averages 15.2 inches of snowfall a year, with January the snowiest month on the normals, spread across roughly 13 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: 15.2 inches of depth.
- Days recording measurable snow: about 13 a year.
- At a rough ten-to-one melt ratio, snow accounts for on the order of 4% 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 21
50% probability date
Last Spring Freeze
April 13
50% probability date
Growing Season
191 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
5,644
Higher = more heating needed
Cooling Degree Days
1,056
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside IL closest to Petersburg 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 (52°F here).
- Albany, MO 52°F · 0.0°F off
- Avondale, PA 52°F · 0.0°F off
- Benkelman, NE 52°F · 0.0°F off
- Bremerton, WA 52°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (37.6" here), excluding temperature-peer places.
- Norman, OK 37.6" · 0.0" off
- Kenton, OH 37.6" · 0.0" off
- Cedar Creek, TX 37.7" · 0.0" off
- Cleburne, TX 37.7" · 0.0" off
Snow and freeze rhythm
When cold and snow define Petersburg
heating led · moderate · mid swing
Petersburg's energy balance leans toward cold weather: 5,644 annual heating degree days against 1,056 for cooling. Its 49.6°F seasonal range still makes the monthly rows more useful than the annual average alone.
Petersburg's frost-free season lasts about 191 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
-
1. Petersburg coldest normal
January
The monthly mean of 26°F (-3°C) sits near freezing, so cold nights and above-freezing afternoons share the same month.
-
2. Petersburg typical freeze period
January through December
The station reports average freezing days from January through December.
-
3. Petersburg snow peak
January
Petersburg averages 15.2 inches of snow a year, with January the snowiest month on the normals.
Questions about Petersburg's climate
How much snow does Petersburg get? ▼
How cold does Petersburg get in winter? ▼
How much energy does heating and cooling require in Petersburg? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Petersburg's primary station: PETERSBURG 1E (USC00116765). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The 2024 Census Gazetteer identifies the exact name-and-state match as an incorporated place (GEOID 1759312). Match rule for Petersburg: exact normalized name + state only, no fuzzy expansion, so nearby differently spelled facilities stay unmatched.
On this page every temperature, precipitation, and derived score for Petersburg 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.