Sigourney, Iowa climate: Normal weather by month, frost dates and records
Sigourney's normal year runs from 12°F January nights to 85°F July afternoons, with 37.4 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.4°C, January lows of −11°C, July highs of 29°C, 950 mm of precipitation a year.
- NOAA stationSigourney
- Station IDUSC00137678
- Location41.34°N 92.23°W
- Elevation732 ft (223 m)
- From the center1 miles
- Population1,974
On October 23, the normal high in Sigourney is 60°F and the normal low 37°F, and the chance of measurable rain or snow is 24%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Sigourney.
- Jan 30° 12°
- Feb 35° 15°
- Mar 48° 26°
- Apr 61° 37°
- May 71° 49°
- Jun 81° 59°
- Jul 85° 63°
- Aug 83° 60°
- Sep 76° 52°
- Oct 63° 40°
- Nov 48° 28°
- Dec 35° 18°
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 Sigourney each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 12°F. The most precipitation falls in June (5.11 in), the least in January (1.18 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 30°F | 12°F | 20.7°F | 1.18 | 6 | <1 | 30 | 9 h 30 min |
| February | 35°F | 15°F | 24.8°F | 1.47 | 6 | <1 | 26 | 10 h 40 min |
| March | 48°F | 26°F | 37.0°F | 2.34 | 7 | <1 | 23 | 11 h 50 min |
| April | 61°F | 37°F | 48.9°F | 3.70 | 9 | <1 | 8 | 13 h 20 min |
| May | 71°F | 49°F | 60.0°F | 4.95 | 12 | <1 | <1 | 14 h 30 min |
| June | 81°F | 59°F | 69.8°F | 5.11 | 12 | 2 | <1 | 15 h 10 min |
| July | 85°F | 63°F | 73.6°F | 3.93 | 8 | 7 | <1 | 14 h 50 min |
| August | 83°F | 60°F | 71.6°F | 4.76 | 9 | 4 | <1 | 13 h 50 min |
| September | 76°F | 52°F | 64.1°F | 3.47 | 7 | 2 | <1 | 12 h 30 min |
| October | 63°F | 40°F | 51.6°F | 2.78 | 8 | <1 | 6 | 11 h 10 min |
| November | 48°F | 28°F | 38.0°F | 2.18 | 7 | <1 | 20 | 9 h 50 min |
| December | 35°F | 18°F | 26.5°F | 1.54 | 6 | <1 | 29 | 9 h 10 min |
| Year (annual) | 60°F | 38°F | 48.9°F | 37.41 | 97 | 16 | 142 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −11°C | −6.3°C | 30 mm |
| February | 1°C | −9°C | −4.0°C | 37 mm |
| March | 9°C | −3°C | 2.8°C | 59 mm |
| April | 16°C | 3°C | 9.4°C | 94 mm |
| May | 22°C | 10°C | 15.6°C | 126 mm |
| June | 27°C | 15°C | 21.0°C | 130 mm |
| July | 29°C | 17°C | 23.1°C | 100 mm |
| August | 28°C | 16°C | 22.0°C | 121 mm |
| September | 25°C | 11°C | 17.8°C | 88 mm |
| October | 17°C | 4°C | 10.9°C | 71 mm |
| November | 9°C | −2°C | 3.3°C | 55 mm |
| December | 2°C | −8°C | −3.1°C | 39 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Ottumwa (20 miles away), gets 24 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00137678; 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 Sigourney?
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 (7).
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 USC00137678.
When is the last frost in Sigourney?
In Sigourney, the last spring frost (32°F) comes after April 24 in half of years and after May 9 in one year in ten; the first autumn frost comes before October 15 in half of years and before September 30 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 241 year in 10 after May 9; 9 in 10 after April 9
- First autumn frost, half of years before
- October 151 year in 10 before September 30; 9 in 10 before October 27
NOAA puts the median frost-free season at 172 days, and the season without a hard freeze (28°F) at 194 days.
A hard freeze (28°F) comes after April 12 in half of springs and before October 24 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Sigourney in zone 5b in ZIP code 52591, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Sigourney's NOAA station is in zone 5b: the coldest night of a typical year reaches −13°F (25 complete years).
Frost dates for every NOAA station in Iowa · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00137678; 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 Sigourney?
In a normal year in Sigourney, 16 days a year reach 90°F (1 of them 100°F or more), 142 nights fall to 32°F or colder and 97 days bring measurable precipitation.
- Days at 90°F or more
- 16a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 142a normal year
- Days that stay below freezing
- 50high of 32°F or less
- Days with 0.01 inch of precipitation
- 97a normal year
The highest temperature in this station's record (since 1896) is 113°F, on July 22, 1901; the lowest is −30°F, on February 13, 1905.
The wettest calendar year on that record is 1993, with 56.36 in; the snowiest season is 1961–62, with 58.3 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00137678; records: ACIS (NOAA Regional Climate Centers), station USC00137678. Records use complete months only; a month missing more than three days is left out.
How sunny is Sigourney?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Sigourney, 4.1 kWh per square metre a day. July is the sunniest month (81%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 69% | 2.0 |
| February | 74% | 3.0 |
| March | 70% | 3.8 |
| April | 70% | 4.8 |
| May | 72% | 5.6 |
| June | 77% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 81% | 4.6 |
| October | 73% | 3.1 |
| November | 71% | 2.1 |
| December | 66% | 1.6 |
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 Sigourney need?
A normal year in Sigourney brings 6,641 heating degree days, 24% more than the median U.S. place (5,373), and 806 cooling degree days, 11% 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 3,046 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,375 | 0 |
| February | 1,124 | 0 |
| March | 871 | 1 |
| April | 486 | 5 |
| May | 199 | 45 |
| June | 27 | 173 |
| July | 3 | 272 |
| August | 11 | 215 |
| September | 114 | 85 |
| October | 426 | 10 |
| November | 812 | 0 |
| December | 1,194 | 0 |
| Year (annual) | 6,641 | 806 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00137678. 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.
Has Sigourney been warmer than normal lately?
2025 averaged 51.3°F, 2.4°F above the 1991-2020 normal of 48.9°F.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2025 | 51.3°F | +2.4°F | 34.67 |
Over 92 complete years from 1897 to 2025, the station's annual mean temperature rose at a fitted 1.3°F per century (+0.07°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00137678; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Sigourney's climate compare?
Sigourney is warmer than 85 of the other 131 places with their own NOAA record in Iowa, and wetter than 81. Across the 7,247 U.S. stations with normals, its annual mean of 48.9°F is warmer than 36%.
In the Köppen classification computed from these normals, Sigourney 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 Sigourney share this climate record?
12 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.
- What Cheer, IA595 people · 8 mi NW
- Delta, IA257 people · 5 mi W
- Deep River, IA243 people · 18 mi NW
- Keswick, IA238 people · 8 mi N
- Ollie, IA196 people · 12 mi SE
- South English, IA196 people · 11 mi NE
- Harper, IA117 people · 9 mi E
- Martinsburg, IA109 people · 11 mi S
- Webster, IA94 people · 8 mi NE
- Gibson, IA58 people · 13 mi NW
- Thornburg, IA46 people · 10 mi NW
- Hayesville, IA43 people · 5 mi S
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 Sigourney's climate
What is the coldest month in Sigourney?
January, with a normal high of 30°F and a normal low of 12°F. The warmest is July (85°F by day, 63°F at night).
Does it snow in Sigourney?
Yes. NOAA publishes no 1991-2020 snowfall normal for Sigourney's NOAA station; the nearest record that keeps one, Ottumwa (20 miles away), records 24 inches of snow in a normal year.
What is the rainiest month in Sigourney?
June, with 5.11 in of precipitation in a normal year; the driest is January with 1.18 in.
What plant hardiness zone is Sigourney in?
The USDA's 2023 map puts Sigourney in zone 5b in ZIP code 52591, the nearest ZIP area. By the same method at Sigourney's NOAA station, the coldest night of a typical year reaches −13°F (25 years, 1991-2020): zone 5b.
How late can frost come in Sigourney?
In half of years the last 32°F night comes after April 24; in one year in ten it comes after May 9. Waiting until May 9 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Ottumwa, IA19 miles from this station, 50.7°F a year
- Oskaloosa, IA22 miles from this station, 50.1°F a year
- Williamsburg, IA25 miles from this station, 48.2°F a year
- Fairfield, IA26 miles from this station, 49.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made