Crystal Lake, IL Climate: Temperature & Rain by Month
Explore NOAA NCEI's 1991–2020 climate normals → and a clearly labeled PlainClimate comfort calculation
30-year climate normals (1991-2020) from Crystal Lake's primary NOAA station, CRYSTAL LAKE 4NW.
The climate verdict for Crystal Lake
Crystal Lake, Illinois has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 49°F. Its climate comfort score of 59/100 (moderate) lands mid-pack nationally, exceeding 37% of station-mapped location scores.
- 49°F
- average temperature, NOAA 1991-2020 normal
- 59/100
- comfort score, above 37% of station-mapped location scores
- 39.4"
- annual precipitation · 35" snow
- 180 days
- frost-free growing season
Crystal Lake: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00112048 · Crystal Lake, IL 49°F mean · 39.4" precip
TEMP-COOL · RANK-COOL · PHOTO-FINISH · PRCP-MID · SWING-WIDE · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 49°F
- RANK-COOL #2,470
- PHOTO-FINISH ≈ Tully Lake
- PRCP-MID 39.4"
- SWING-WIDE 50°F
- COMF-MID 59/100
- LOAD-HEAT 6,520 HDD
- STN-1 USC00112048
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Tully Lake, MA (+ 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.
- Crystal Lake (this station) 49°F
- Hot Lisle-morton Ar…, IL 49°F
- Near Tully Lake, MA 49°F
- Near Scottsbluff, NE 49°F
- Near Saint Johns, MI 49°F
Climate Living Index · Crystal Lake
Crystal Lake: 51/100 · grade D
Crystal Lake publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Crystal Lake, not an official NOAA rating. Rankings still use Comfort Score 59/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 39.4 in · 4.4 from 35 in | 84/100 · B |
| Normal heat + freeze calendar | 140 calendar days | 53/100 · D |
| Frost-free season | 180 days/year | 50/100 · D |
| Annual temperature balance | 49.1°F · 18.4° from 67.5°F | 36/100 · F |
| Snowfall burden | 35.1 inches/year | 33/100 · F |
Crystal Lake · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Crystal Lake is a continental Köppen climate: Dfa
Coldest-month mean 22.9°F and warmest-month mean 73.3°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
- 73.3°F
- Coldest month
- 22.9°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 Crystal Lake sits across the climate record
Three NOAA fields for Crystal Lake's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 36th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 56th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Wider than 82%
- Warmest-to-coldest month gap for Crystal Lake is large versus 6,861 complete station-years.
How Crystal Lake compares across U.S. station-mapped locations
Crystal Lake's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
59 37th percentile score exceeds 37% 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%). This entry sits in this band.
- 60–70: 1,236 station-mapped locations (20%). Above this entry.
- 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 | 32°F (0°C) | 14°F (-10°C) | 23°F (-5°C) | 2.0" | 10.0" | 28.9 | 0.0 |
| February | 35°F (2°C) | 16°F (-9°C) | 26°F (-3°C) | 1.8" | 9.0" | 27.2 | 0.0 |
| March | 47°F (8°C) | 26°F (-3°C) | 37°F (3°C) | 2.5" | 4.4" | 22.1 | 0.0 |
| April | 59°F (15°C) | 37°F (3°C) | 48°F (9°C) | 3.8" | 1.2" | 9.1 | 0.0 |
| May | 71°F (22°C) | 48°F (9°C) | 60°F (15°C) | 5.0" | 0.0" | 0.3 | 2.1 |
| June | 80°F (27°C) | 58°F (15°C) | 69°F (21°C) | 5.3" | 0.0" | 0.0 | 5.5 |
| July | 84°F (29°C) | 63°F (17°C) | 73°F (23°C) | 3.9" | 0.0" | 0.0 | 7.7 |
| August | 82°F (28°C) | 61°F (16°C) | 72°F (22°C) | 3.8" | 0.0" | 0.0 | 4.0 |
| September | 74°F (24°C) | 52°F (11°C) | 63°F (17°C) | 3.5" | 0.0" | 0.0 | 2.5 |
| October | 62°F (17°C) | 42°F (6°C) | 52°F (11°C) | 3.2" | 0.2" | 3.4 | 0.0 |
| November | 48°F (9°C) | 31°F (-1°C) | 39°F (4°C) | 2.5" | 1.6" | 18.0 | 0.0 |
| December | 36°F (2°C) | 20°F (-6°C) | 28°F (-2°C) | 2.1" | 8.7" | 26.5 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 85°F around July 24, short of 90°F on every date, while 140 dates carry a normal low at or below freezing, the coldest 14°F near January 18.
The freezing stretch
The normal low stays at or below 32°F into March 29, then returns to freezing around November 11, covering 140 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 8, when 39% of years recorded at least a hundredth of an inch. The driest is September 1 at 26%. Summed across the calendar, that is about 110 wet dates a year.
The widest day
May 9 carries the biggest normal gap between afternoon and dawn, 24°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Crystal Lake.
Monthly Precipitation
Average monthly rainfall and snowfall
Snow: 10.0"
8.6 days with precipitation
Snow: 9.0"
7.6 days with precipitation
Snow: 4.4"
8.3 days with precipitation
Snow: 1.2"
11.0 days with precipitation
11.8 days with precipitation
9.9 days with precipitation
8.5 days with precipitation
8.9 days with precipitation
8.0 days with precipitation
Snow: 0.2"
9.4 days with precipitation
Snow: 1.6"
8.5 days with precipitation
Snow: 8.7"
9.2 days with precipitation
Crystal Lake spreads its precipitation across the year
Neither half of the year dominates here: June through August take 33% of the annual total and December through February 15%, with neither reaching the 35% that would mark a distinct wet season. Crystal Lake has no dry season to plan around, though it does carry a wide 50.4°F gap between its warmest and coldest month.
The gap between the wettest and driest month still matters: June averages 5.3" and February 1.8". The three wettest months together take 36% 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 Crystal Lake, it arrives in quantity
39.3" of precipitation falls across only about 110 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 110 a year, 30% of all days
- Average depth per wet day
- 0.36 inches
- Most wet days
- May, about 12
- Fewest wet days
- February, about 8
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 Crystal Lake
Crystal Lake averages 35.1 inches of snowfall a year, with January the snowiest month on the normals, spread across roughly 22 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: 35.1 inches of depth.
- Days recording measurable snow: about 22 a year.
- At a rough ten-to-one melt ratio, snow accounts for on the order of 9% 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 22
50% probability date
Last Spring Freeze
April 25
50% probability date
Growing Season
180 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
6,520
Higher = more heating needed
Cooling Degree Days
771
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside IL closest to Crystal Lake 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 (49°F here).
- Arlington, WA 49°F · 0.0°F off
- Byers, CO 49°F · 0.0°F off
- Greenfield, IA 49°F · 0.0°F off
- Lockport, NY 49°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (39.4" here), excluding temperature-peer places.
- Fort Madison, IA 39.4" · 0.0" off
- Meeker, OK 39.4" · 0.0" off
- Seattle, WA 39.3" · 0.0" off
- Webster, NY 39.3" · 0.0" off
Snow and freeze rhythm
When cold and snow define Crystal Lake
heating led · moderate · mid swing
Crystal Lake's energy balance leans toward cold weather: 6,520 annual heating degree days against 771 for cooling. Its 50.4°F seasonal range still makes the monthly rows more useful than the annual average alone.
Crystal Lake's frost-free season lasts about 180 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
-
1. Crystal Lake coldest normal
January
Averaging 23°F (-5°C), this month sits below freezing for the month as a whole, not merely overnight.
-
2. Crystal Lake typical freeze period
January through December
The station reports average freezing days from January through December.
-
3. Crystal Lake snow peak
January
Crystal Lake averages 35.1 inches of snow a year, with January the snowiest month on the normals.
Questions about Crystal Lake's climate
How much snow does Crystal Lake get? ▼
How cold does Crystal Lake get in winter? ▼
How much energy does heating and cooling require in Crystal Lake? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Crystal Lake's primary station: CRYSTAL LAKE 4NW (USC00112048). 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 1717887). Match rule for Crystal Lake: 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 Crystal Lake 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.