Polo, Illinois climate: Normal weather by month, frost dates and records
Polo's normal year runs from 13°F January nights to 85°F July afternoons, with 40.0 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.6°C, January lows of −10°C, July highs of 29°C, 1,017 mm of precipitation a year.
- NOAA stationPolo (5 mi NW)
- Station IDUSC00116897
- Location42.03°N 89.61°W
- Elevation856 ft (261 m)
- From the center4 miles
- Population2,238
On October 23, the normal high in Polo is 61°F and the normal low 38°F, and the chance of measurable rain or snow is 30%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Polo.
- Jan 30° 13°
- Feb 35° 17°
- Mar 48° 28°
- Apr 61° 38°
- May 73° 49°
- Jun 82° 59°
- Jul 85° 62°
- Aug 83° 59°
- Sep 77° 51°
- Oct 64° 40°
- Nov 48° 29°
- Dec 35° 19°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Polo each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 13°F. The most precipitation falls in June (5.07 in), the least in January (1.94 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 30°F | 13°F | 21.7°F | 1.94 | 11 | <1 | 29 | 9 h 30 min |
| February | 35°F | 17°F | 25.7°F | 1.95 | 9 | <1 | 26 | 10 h 30 min |
| March | 48°F | 28°F | 37.6°F | 2.79 | 11 | <1 | 22 | 11 h 50 min |
| April | 61°F | 38°F | 49.4°F | 3.85 | 12 | <1 | 8 | 13 h 20 min |
| May | 73°F | 49°F | 61.1°F | 4.72 | 14 | 1 | 1 | 14 h 30 min |
| June | 82°F | 59°F | 70.5°F | 5.07 | 12 | 4 | <1 | 15 h 10 min |
| July | 85°F | 62°F | 73.0°F | 4.40 | 10 | 6 | <1 | 15 h |
| August | 83°F | 59°F | 71.0°F | 3.71 | 10 | 3 | <1 | 14 h |
| September | 77°F | 51°F | 64.0°F | 3.59 | 8 | 2 | 1 | 12 h 30 min |
| October | 64°F | 40°F | 52.1°F | 3.21 | 9 | <1 | 7 | 11 h 10 min |
| November | 48°F | 29°F | 38.7°F | 2.65 | 10 | <1 | 18 | 9 h 50 min |
| December | 35°F | 19°F | 27.2°F | 2.14 | 11 | <1 | 27 | 9 h 10 min |
| Year (annual) | 60°F | 39°F | 49.3°F | 40.02 | 125 | 17 | 138 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −10°C | −5.7°C | 49 mm |
| February | 2°C | −8°C | −3.5°C | 50 mm |
| March | 9°C | −2°C | 3.1°C | 71 mm |
| April | 16°C | 3°C | 9.7°C | 98 mm |
| May | 23°C | 10°C | 16.2°C | 120 mm |
| June | 28°C | 15°C | 21.4°C | 129 mm |
| July | 29°C | 16°C | 22.8°C | 112 mm |
| August | 28°C | 15°C | 21.7°C | 94 mm |
| September | 25°C | 11°C | 17.8°C | 91 mm |
| October | 18°C | 5°C | 11.2°C | 82 mm |
| November | 9°C | −1°C | 3.7°C | 67 mm |
| December | 2°C | −7°C | −2.7°C | 54 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Dixon (15 miles away), gets 31 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00116897; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Polo?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (8).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00116897.
When is the last frost in Polo?
In Polo, the last spring frost (32°F) comes after April 29 in half of years and after May 14 in one year in ten; the first autumn frost comes before October 7 in half of years and before September 23 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 291 year in 10 after May 14; 9 in 10 after April 15
- First autumn frost, half of years before
- October 71 year in 10 before September 23; 9 in 10 before October 22
NOAA puts the median frost-free season at 161 days, and the season without a hard freeze (28°F) at 183 days.
A hard freeze (28°F) comes after April 19 in half of springs and before October 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Polo in zone 5b in ZIP code 61064, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Polo's NOAA station is in zone 5a: the coldest night of a typical year reaches −16°F (21 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Illinois · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00116897; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Polo?
In a normal year in Polo, 17 days a year reach 90°F, 138 nights fall to 32°F or colder and 125 days bring measurable precipitation.
- Days at 90°F or more
- 17a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 138a normal year
- Days that stay below freezing
- 45high of 32°F or less
- Days with 0.01 inch of precipitation
- 125a normal year
The highest temperature in this station's record (since 1995) is 102°F, on July 7, 2012; the lowest is −32°F, on January 16, 2009.
The wettest calendar year on that record is 2009, with 58.57 in; the snowiest season is 2008–09, with 53.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00116897; records: ACIS (NOAA Regional Climate Centers), station USC00116897. Records use complete months only; a month missing more than three days is left out.
How sunny is Polo?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Polo, 3.9 kWh per square metre a day. July is the sunniest month (80%) and December the cloudiest (61%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 66% | 1.8 |
| February | 70% | 2.8 |
| March | 69% | 3.8 |
| April | 68% | 4.7 |
| May | 71% | 5.5 |
| June | 76% | 6.2 |
| July | 80% | 6.3 |
| August | 79% | 5.5 |
| September | 78% | 4.4 |
| October | 70% | 2.9 |
| November | 67% | 1.9 |
| December | 61% | 1.4 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Polo need?
A normal year in Polo brings 6,466 heating degree days, 20% more than the median U.S. place (5,373), and 799 cooling degree days, 12% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,067 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,342 | 0 |
| February | 1,099 | 0 |
| March | 849 | 1 |
| April | 473 | 5 |
| May | 180 | 61 |
| June | 24 | 189 |
| July | 5 | 254 |
| August | 11 | 197 |
| September | 112 | 82 |
| October | 411 | 11 |
| November | 788 | 0 |
| December | 1,173 | 0 |
| Year (annual) | 6,466 | 799 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00116897. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
How does Polo's climate compare?
Polo is warmer than 21 of the other 143 places with their own NOAA record in Illinois, and wetter than 73. Across the 7,247 U.S. stations with normals, its annual mean of 49.3°F is warmer than 37%.
In the Köppen classification computed from these normals, Polo is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Polo share this climate record?
7 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Oregon, IL3,570 people · 14 mi E
- Mount Morris, IL2,792 people · 9 mi E
- Forreston, IL1,403 people · 7 mi N
- Milledgeville, IL992 people · 10 mi SW
- Shannon, IL841 people · 11 mi NW
- Leaf River, IL419 people · 12 mi NE
- Adeline, IL75 people · 9 mi NE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Polo's climate
What is the coldest month in Polo?
January, with a normal high of 30°F and a normal low of 13°F. The warmest is July (85°F by day, 62°F at night).
Does it snow in Polo?
Yes. NOAA publishes no 1991-2020 snowfall normal for Polo's NOAA station; the nearest record that keeps one, Dixon (15 miles away), records 31 inches of snow in a normal year.
What is the rainiest month in Polo?
June, with 5.07 in of precipitation in a normal year; the driest is January with 1.94 in.
What plant hardiness zone is Polo in?
The USDA's 2023 map puts Polo in zone 5b in ZIP code 61064, the nearest ZIP area. By the same method at Polo's NOAA station, the coldest night of a typical year reaches −16°F (21 years, 1991-2020): zone 5a.
How late can frost come in Polo?
In half of years the last 32°F night comes after April 29; in one year in ten it comes after May 14. Waiting until May 14 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Dixon, IL14 miles from this station, 49.4°F a year
- Freeport, IL18 miles from this station, 47.7°F a year
- Mount Carroll, IL20 miles from this station, 48.5°F a year
- Morrison, IL25 miles from this station, 48.3°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made