Harlan, Iowa climate: Normal weather by month, frost dates and records
Harlan's normal year runs from 10°F January nights to 86°F July afternoons, with 34.3 inches of precipitation and 31 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.7°C, January lows of −12°C, July highs of 30°C, 872 mm of precipitation a year.
- NOAA stationHarlan
- Station IDUSC00133632
- Location41.65°N 95.33°W
- Elevation1,270 ft (387 m)
- From the centerunder 1 mile
- Population4,898
On October 23, the normal high in Harlan is 62°F and the normal low 36°F, and the chance of measurable rain or snow is 22%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Harlan.
- Jan 31° 10°
- Feb 36° 14°
- Mar 50° 25°
- Apr 63° 36°
- May 74° 49°
- Jun 84° 60°
- Jul 86° 64°
- Aug 84° 61°
- Sep 79° 52°
- Oct 65° 39°
- Nov 49° 26°
- Dec 36° 16°
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 Harlan each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 10°F. The most precipitation falls in June (5.17 in), the least in January (0.90 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 31°F | 10°F | 20.5°F | 0.90 | 7.6 | 6 | <1 | 30 | 9 h 30 min |
| February | 36°F | 14°F | 24.7°F | 0.98 | 7.6 | 7 | <1 | 26 | 10 h 30 min |
| March | 50°F | 25°F | 37.6°F | 2.05 | 4.0 | 7 | <1 | 23 | 11 h 50 min |
| April | 63°F | 36°F | 49.8°F | 3.34 | 1.5 | 11 | <1 | 9 | 13 h 20 min |
| May | 74°F | 49°F | 61.7°F | 4.74 | 0.0 | 12 | 1 | 1 | 14 h 30 min |
| June | 84°F | 60°F | 71.7°F | 5.17 | 0.0 | 11 | 4 | <1 | 15 h 10 min |
| July | 86°F | 64°F | 74.7°F | 3.72 | 0.0 | 9 | 7 | <1 | 15 h |
| August | 84°F | 61°F | 72.4°F | 4.32 | 0.0 | 9 | 4 | <1 | 13 h 50 min |
| September | 79°F | 52°F | 65.1°F | 4.00 | 0.0 | 7 | 2 | <1 | 12 h 30 min |
| October | 65°F | 39°F | 52.2°F | 2.37 | 0.9 | 8 | <1 | 8 | 11 h 10 min |
| November | 49°F | 26°F | 37.6°F | 1.43 | 2.2 | 6 | <1 | 22 | 9 h 50 min |
| December | 36°F | 16°F | 25.8°F | 1.31 | 6.7 | 6 | <1 | 29 | 9 h 10 min |
| Year (annual) | 61°F | 38°F | 49.5°F | 34.33 | 30.5 | 98 | 19 | 148 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −12°C | −6.4°C | 23 mm | 19 cm |
| February | 2°C | −10°C | −4.1°C | 25 mm | 19 cm |
| March | 10°C | −4°C | 3.1°C | 52 mm | 10 cm |
| April | 17°C | 2°C | 9.9°C | 85 mm | 4 cm |
| May | 23°C | 10°C | 16.5°C | 120 mm | 0 cm |
| June | 29°C | 16°C | 22.1°C | 131 mm | 0 cm |
| July | 30°C | 18°C | 23.7°C | 94 mm | 0 cm |
| August | 29°C | 16°C | 22.4°C | 110 mm | 0 cm |
| September | 26°C | 11°C | 18.4°C | 102 mm | 0 cm |
| October | 19°C | 4°C | 11.2°C | 60 mm | 2 cm |
| November | 10°C | −3°C | 3.1°C | 36 mm | 6 cm |
| December | 2°C | −9°C | −3.4°C | 33 mm | 17 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00133632; 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 Harlan?
Normal highs sit between 65°F and 85°F in May, June, August, September and October. 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 USC00133632.
When is the last frost in Harlan?
In Harlan, the last spring frost (32°F) comes after April 27 in half of years and after May 9 in one year in ten; the first autumn frost comes before October 9 in half of years and before September 24 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 271 year in 10 after May 9; 9 in 10 after April 12
- First autumn frost, half of years before
- October 91 year in 10 before September 24; 9 in 10 before October 22
NOAA puts the median frost-free season at 165 days, and the season without a hard freeze (28°F) at 184 days.
A hard freeze (28°F) comes after April 17 in half of springs and before October 20 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Harlan in zone 5b in ZIP code 51537, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Harlan's NOAA station is in zone 5b: the coldest night of a typical year reaches −14°F (23 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 USC00133632; 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 Harlan?
In a normal year in Harlan, 19 days a year reach 90°F, 148 nights fall to 32°F or colder and 98 days bring measurable precipitation.
- Days at 90°F or more
- 19a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 148a normal year
- Days that stay below freezing
- 52high of 32°F or less
- Days with 0.01 inch of precipitation
- 98a normal year
- Days with 1 inch of snow or more
- 9a normal year
The highest temperature in this station's record (since 1899) is 114°F, on July 25, 1936; the lowest is −37°F, on January 12, 1912.
The wettest calendar year on that record is 1972, with 47.30 in; the snowiest season is 1961–62, with 62.6 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00133632; records: ACIS (NOAA Regional Climate Centers), station USC00133632. Records use complete months only; a month missing more than three days is left out.
How sunny is Harlan?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Harlan, 4.2 kWh per square metre a day. July is the sunniest month (83%) and December the cloudiest (69%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 69% | 2.0 |
| February | 74% | 3.0 |
| March | 69% | 3.8 |
| April | 70% | 4.9 |
| May | 73% | 5.8 |
| June | 79% | 6.5 |
| July | 83% | 6.5 |
| August | 81% | 5.6 |
| September | 81% | 4.6 |
| October | 75% | 3.2 |
| November | 74% | 2.3 |
| December | 69% | 1.7 |
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 Harlan need?
A normal year in Harlan brings 6,566 heating degree days, 22% more than the median U.S. place (5,373), and 957 cooling degree days, 5% more 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 3,280 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,379 | 0 |
| February | 1,128 | 0 |
| March | 851 | 1 |
| April | 462 | 8 |
| May | 171 | 68 |
| June | 18 | 220 |
| July | 3 | 306 |
| August | 10 | 239 |
| September | 98 | 100 |
| October | 410 | 15 |
| November | 822 | 0 |
| December | 1,215 | 0 |
| Year (annual) | 6,566 | 957 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00133632. 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 Harlan's climate compare?
Harlan is warmer than 97 of the other 131 places with their own NOAA record in Iowa, and wetter than 34. Across the 7,247 U.S. stations with normals, its annual mean of 49.5°F is warmer than 38%.
In the Köppen classification computed from these normals, Harlan 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 Harlan 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.
- Avoca, IA1,685 people · 11 mi S
- Shelby, IA730 people · 11 mi SW
- Earling, IA394 people · 10 mi NW
- Irwin, IA320 people · 12 mi NE
- Defiance, IA248 people · 12 mi N
- Panama, IA234 people · 9 mi NW
- Portsmouth, IA187 people · 10 mi W
- Westphalia, IA133 people · 6 mi NW
- Tennant, IA83 people · 7 mi SW
- Kirkman, IA60 people · 7 mi NE
- Corley, IA7 people · 5 mi S
- Jacksonville, IA6 people · 9 mi E
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 Harlan's climate
What is the coldest month in Harlan?
January, with a normal high of 31°F and a normal low of 10°F. The warmest is July (86°F by day, 64°F at night).
Does it snow in Harlan?
Yes: 31 inches in a normal year, falling on 19 days with 0.1 inch or more, the most in January (7.6 inches).
What is the rainiest month in Harlan?
June, with 5.17 in of precipitation in a normal year; the driest is January with 0.90 in.
What plant hardiness zone is Harlan in?
The USDA's 2023 map puts Harlan in zone 5b in ZIP code 51537, the nearest ZIP area. By the same method at Harlan's NOAA station, the coldest night of a typical year reaches −14°F (23 years, 1991-2020): zone 5b.
How late can frost come in Harlan?
In half of years the last 32°F night comes after April 27; 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
- Audubon, IA22 miles from this station, 47.0°F a year
- Atlantic, IA23 miles from this station, 49.3°F a year
- Logan, IA24 miles from this station, 49.1°F a year
- Oakland, IA24 miles from this station, 49.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made