Decorah, Iowa climate: Normal weather by month, frost dates and records
Decorah's normal year runs from 10°F January nights to 84°F July afternoons, with 37.6 inches of precipitation and 38 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.2°C, January lows of −12°C, July highs of 29°C, 955 mm of precipitation a year.
- NOAA stationDecorah
- Station IDUSC00132110
- Location43.30°N 91.80°W
- Elevation860 ft (262 m)
- Population7,454
On October 23, the normal high in Decorah is 60°F and the normal low 38°F, and the chance of measurable rain or snow is 28%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Decorah.
- Jan 28° 10°
- Feb 33° 14°
- Mar 46° 26°
- Apr 61° 37°
- May 73° 48°
- Jun 81° 59°
- Jul 84° 63°
- Aug 83° 61°
- Sep 76° 52°
- Oct 63° 40°
- Nov 47° 28°
- Dec 33° 17°
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 Decorah each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 10°F. The most precipitation falls in June (6.13 in), the least in January (1.01 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 28°F | 10°F | 19.0°F | 1.01 | 10.3 | 8 | <1 | 30 | 9 h 20 min |
| February | 33°F | 14°F | 23.4°F | 1.10 | 8.3 | 6 | <1 | 27 | 10 h 30 min |
| March | 46°F | 26°F | 36.0°F | 2.05 | 5.7 | 8 | <1 | 24 | 11 h 50 min |
| April | 61°F | 37°F | 49.3°F | 3.95 | 1.7 | 12 | <1 | 11 | 13 h 20 min |
| May | 73°F | 48°F | 60.5°F | 4.94 | 0.0 | 13 | 1 | 2 | 14 h 40 min |
| June | 81°F | 59°F | 70.0°F | 6.13 | 0.0 | 12 | 3 | <1 | 15 h 20 min |
| July | 84°F | 63°F | 73.5°F | 4.42 | 0.0 | 10 | 5 | <1 | 15 h 10 min |
| August | 83°F | 61°F | 71.7°F | 4.39 | 0.0 | 10 | 3 | <1 | 14 h |
| September | 76°F | 52°F | 64.4°F | 3.60 | 0.0 | 9 | 1 | 1 | 12 h 30 min |
| October | 63°F | 40°F | 51.8°F | 2.66 | 0.0 | 9 | <1 | 9 | 11 h 10 min |
| November | 47°F | 28°F | 37.5°F | 2.05 | 2.4 | 8 | <1 | 21 | 9 h 40 min |
| December | 33°F | 17°F | 25.2°F | 1.31 | 9.1 | 8 | <1 | 29 | 9 h |
| Year (annual) | 59°F | 38°F | 48.5°F | 37.61 | 37.5 | 114 | 12 | 153 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −2°C | −12°C | −7.2°C | 26 mm | 26 cm |
| February | 0°C | −10°C | −4.8°C | 28 mm | 21 cm |
| March | 8°C | −3°C | 2.2°C | 52 mm | 14 cm |
| April | 16°C | 3°C | 9.6°C | 100 mm | 4 cm |
| May | 23°C | 9°C | 15.8°C | 125 mm | 0 cm |
| June | 27°C | 15°C | 21.1°C | 156 mm | 0 cm |
| July | 29°C | 17°C | 23.1°C | 112 mm | 0 cm |
| August | 28°C | 16°C | 22.1°C | 112 mm | 0 cm |
| September | 25°C | 11°C | 18.0°C | 91 mm | 0 cm |
| October | 17°C | 5°C | 11.0°C | 68 mm | 0 cm |
| November | 8°C | −2°C | 3.1°C | 52 mm | 6 cm |
| December | 0°C | −8°C | −3.8°C | 33 mm | 23 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00132110; 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 Decorah?
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 (9).
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 USC00132110.
When is the last frost in Decorah?
In Decorah, the last spring frost (32°F) comes after May 3 in half of years and after May 16 in one year in ten; the first autumn frost comes before October 7 in half of years and before September 25 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
- May 31 year in 10 after May 16; 9 in 10 after April 19
- First autumn frost, half of years before
- October 71 year in 10 before September 25; 9 in 10 before October 21
NOAA puts the median frost-free season at 157 days, and the season without a hard freeze (28°F) at 178 days.
A hard freeze (28°F) comes after April 22 in half of springs and before October 17 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Decorah in zone 5a in ZIP code 52101, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Decorah's NOAA station is in zone 4b: the coldest night of a typical year reaches −22°F (30 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 Iowa · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00132110; 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 Decorah?
In a normal year in Decorah, 12 days a year reach 90°F, 153 nights fall to 32°F or colder and 114 days bring measurable precipitation.
- Days at 90°F or more
- 12a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 153a normal year
- Days that stay below freezing
- 58high of 32°F or less
- Days with 0.01 inch of precipitation
- 114a normal year
- Days with 1 inch of snow or more
- 14a normal year
The highest temperature in this station's record (since 1893) is 111°F, on July 14, 1936; the lowest is −43°F, on January 30, 1951.
The wettest calendar year on that record is 2016, with 57.58 in; the snowiest season is 1961–62, with 69.2 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00132110; records: ACIS (NOAA Regional Climate Centers), station USC00132110. Records use complete months only; a month missing more than three days is left out.
How sunny is Decorah?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Decorah, 3.9 kWh per square metre a day. July is the sunniest month (80%) and December the cloudiest (62%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 69% | 1.8 |
| February | 75% | 2.9 |
| March | 71% | 3.8 |
| April | 67% | 4.6 |
| May | 70% | 5.5 |
| June | 74% | 6.1 |
| July | 80% | 6.3 |
| August | 78% | 5.3 |
| September | 77% | 4.2 |
| October | 69% | 2.8 |
| November | 67% | 1.9 |
| December | 62% | 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 Decorah need?
A normal year in Decorah brings 6,795 heating degree days, 26% more than the median U.S. place (5,373), and 828 cooling degree days, 9% 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 3,070 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,424 | 0 |
| February | 1,165 | 0 |
| March | 899 | 1 |
| April | 478 | 7 |
| May | 193 | 52 |
| June | 28 | 178 |
| July | 4 | 268 |
| August | 11 | 218 |
| September | 111 | 92 |
| October | 421 | 12 |
| November | 825 | 0 |
| December | 1,235 | 0 |
| Year (annual) | 6,795 | 828 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00132110. 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 Decorah been warmer than normal lately?
2025 averaged 49.5°F, 1.0°F above the 1991-2020 normal of 48.5°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 50.4°F | +1.9°F | 29.50 | 34.8 |
| 2022 | 47.4°F | −1.1°F | 39.23 | 29.2 |
| 2023 | 51.6°F | +3.1°F | 28.38 | 28.1 |
| 2024 | 52.5°F | +4.0°F | 38.46 | 21.9 |
| 2025 | 49.5°F | +1.0°F | 43.03 | 25.2 |
Over 105 complete years from 1895 to 2025, the station's annual mean temperature rose at a fitted 1.7°F per century (+0.09°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00132110; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Decorah's climate compare?
Decorah is warmer than 76 of the other 131 places with their own NOAA record in Iowa, and wetter than 83. Across the 7,247 U.S. stations with normals, its annual mean of 48.5°F is warmer than 34%.
In the Köppen classification computed from these normals, Decorah 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 Decorah share this climate record?
4 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.
- Calmar, IA1,100 people · 9 mi SW
- Ossian, IA777 people · 11 mi S
- Spillville, IA371 people · 11 mi SW
- Fort Atkinson, IA300 people · 13 mi SW
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 Decorah's climate
What is the coldest month in Decorah?
January, with a normal high of 28°F and a normal low of 10°F. The warmest is July (84°F by day, 63°F at night).
Does it snow in Decorah?
Yes: 38 inches in a normal year, falling on 23 days with 0.1 inch or more, the most in January (10.3 inches).
What is the rainiest month in Decorah?
June, with 6.13 in of precipitation in a normal year; the driest is January with 1.01 in.
What plant hardiness zone is Decorah in?
The USDA's 2023 map puts Decorah in zone 5a in ZIP code 52101, the nearest ZIP area. By the same method at Decorah's NOAA station, the coldest night of a typical year reaches −22°F (30 years, 1991-2020): zone 4b.
How late can frost come in Decorah?
In half of years the last 32°F night comes after May 3; in one year in ten it comes after May 16. Waiting until May 16 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Mabel, MN16 miles from this station, 43.5°F a year
- Cresco, IA16 miles from this station, 45.0°F a year
- Waukon, IA16 miles from this station, 45.4°F a year
- Postville, IA19 miles from this station, 46.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made