Postville, Iowa climate: Normal weather by month, frost dates and records
Postville's normal year runs from 7°F January nights to 83°F July afternoons, with 38.9 inches of precipitation and 40 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.8°C, January lows of −14°C, July highs of 28°C, 989 mm of precipitation a year.
- NOAA stationPostville
- Station IDUSC00136766
- Location43.09°N 91.56°W
- Elevation1,165 ft (355 m)
- Population2,418
On October 23, the normal high in Postville is 57°F and the normal low 34°F, and the chance of measurable rain or snow is 23%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Postville.
- Jan 26° 7°
- Feb 30° 11°
- Mar 43° 22°
- Apr 58° 34°
- May 69° 47°
- Jun 79° 58°
- Jul 83° 61°
- Aug 81° 58°
- Sep 74° 49°
- Oct 61° 37°
- Nov 45° 26°
- Dec 31° 14°
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 Postville each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 7°F. The most precipitation falls in June (5.88 in), the least in January (1.12 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 26°F | 7°F | 16.6°F | 1.12 | 12.0 | 6 | <1 | 31 | 9 h 20 min |
| February | 30°F | 11°F | 20.2°F | 1.21 | 10.4 | 5 | <1 | 28 | 10 h 30 min |
| March | 43°F | 22°F | 32.7°F | 2.09 | 5.0 | 7 | <1 | 25 | 11 h 50 min |
| April | 58°F | 34°F | 45.8°F | 4.14 | 1.6 | 10 | <1 | 13 | 13 h 20 min |
| May | 69°F | 47°F | 58.2°F | 4.99 | 0.0 | 12 | 1 | 2 | 14 h 40 min |
| June | 79°F | 58°F | 68.4°F | 5.88 | 0.0 | 11 | 2 | <1 | 15 h 20 min |
| July | 83°F | 61°F | 71.9°F | 4.52 | 0.0 | 9 | 4 | <1 | 15 h 10 min |
| August | 81°F | 58°F | 69.5°F | 4.36 | 0.0 | 9 | 2 | <1 | 14 h |
| September | 74°F | 49°F | 61.6°F | 3.96 | 0.0 | 9 | 1 | 1 | 12 h 30 min |
| October | 61°F | 37°F | 48.8°F | 3.00 | 0.1 | 8 | <1 | 10 | 11 h 10 min |
| November | 45°F | 26°F | 35.1°F | 2.10 | 2.7 | 6 | <1 | 23 | 9 h 50 min |
| December | 31°F | 14°F | 22.7°F | 1.57 | 8.0 | 6 | <1 | 30 | 9 h |
| Year (annual) | 57°F | 35°F | 46.0°F | 38.94 | 39.8 | 97 | 9 | 162 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −4°C | −14°C | −8.6°C | 28 mm | 30 cm |
| February | −1°C | −12°C | −6.6°C | 31 mm | 26 cm |
| March | 6°C | −5°C | 0.4°C | 53 mm | 13 cm |
| April | 14°C | 1°C | 7.7°C | 105 mm | 4 cm |
| May | 21°C | 8°C | 14.6°C | 127 mm | 0 cm |
| June | 26°C | 14°C | 20.2°C | 149 mm | 0 cm |
| July | 28°C | 16°C | 22.2°C | 115 mm | 0 cm |
| August | 27°C | 15°C | 20.8°C | 111 mm | 0 cm |
| September | 23°C | 10°C | 16.4°C | 101 mm | 0 cm |
| October | 16°C | 3°C | 9.3°C | 76 mm | 0 cm |
| November | 7°C | −4°C | 1.7°C | 53 mm | 7 cm |
| December | 0°C | −10°C | −5.2°C | 40 mm | 20 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136766; 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 Postville?
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 USC00136766.
When is the last frost in Postville?
In Postville, the last spring frost (32°F) comes after May 1 in half of years and after May 14 in one year in ten; the first autumn frost comes before October 3 in half of years and before September 20 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 11 year in 10 after May 14; 9 in 10 after April 18
- First autumn frost, half of years before
- October 31 year in 10 before September 20; 9 in 10 before October 17
NOAA puts the median frost-free season at 153 days, and the season without a hard freeze (28°F) at 174 days.
A hard freeze (28°F) comes after April 22 in half of springs and before October 12 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Postville in zone 5a in ZIP code 52162, the nearest ZIP area.
Frost dates for every NOAA station in Iowa · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00136766; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Postville?
In a normal year in Postville, 9 days a year reach 90°F, 162 nights fall to 32°F or colder and 97 days bring measurable precipitation.
- Days at 90°F or more
- 9a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 162a normal year
- Days that stay below freezing
- 64high of 32°F or less
- Days with 0.01 inch of precipitation
- 97a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1901) is 108°F, on July 21, 1901; the lowest is −31°F, on January 5, 1924.
The wettest calendar year on that record is 2018, with 53.41 in; the snowiest season is 1992–93, with 70.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00136766; records: ACIS (NOAA Regional Climate Centers), station USC00136766. Records use complete months only; a month missing more than three days is left out.
How sunny is Postville?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Postville, 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 Postville need?
A normal year in Postville brings 7,520 heating degree days, 40% more than the median U.S. place (5,373), and 614 cooling degree days, 32% 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 2,659 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,502 | 0 |
| February | 1,254 | 0 |
| March | 1,002 | 0 |
| April | 578 | 1 |
| May | 246 | 34 |
| June | 37 | 139 |
| July | 9 | 221 |
| August | 22 | 161 |
| September | 155 | 53 |
| October | 508 | 6 |
| November | 897 | 0 |
| December | 1,311 | 0 |
| Year (annual) | 7,520 | 614 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136766. 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 Postville been warmer than normal lately?
2022 averaged 45.3°F, 0.7°F below the 1991-2020 normal of 46.0°F.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2022 | 45.3°F | −0.7°F | 39.09 | 27.0 |
Source: observed years: ACIS, station USC00136766. A year counts only with all twelve months complete.
How does Postville's climate compare?
Postville is warmer than 17 of the other 131 places with their own NOAA record in Iowa, and wetter than 112. Across the 7,247 U.S. stations with normals, its annual mean of 46.0°F is warmer than 23%.
In the Köppen classification computed from these normals, Postville 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 Postville 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.
- Elgin, IA676 people · 10 mi SW
- Clermont, IA571 people · 8 mi SW
- Luana, IA303 people · 6 mi E
- Castalia, IA141 people · 6 mi W
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 Postville's climate
What is the coldest month in Postville?
January, with a normal high of 26°F and a normal low of 7°F. The warmest is July (83°F by day, 61°F at night).
Does it snow in Postville?
Yes: 40 inches in a normal year, falling on 20 days with 0.1 inch or more, the most in January (12.0 inches).
What is the rainiest month in Postville?
June, with 5.88 in of precipitation in a normal year; the driest is January with 1.12 in.
What plant hardiness zone is Postville in?
The USDA's 2023 map puts Postville in zone 5a in ZIP code 52162, the nearest ZIP area.
How late can frost come in Postville?
In half of years the last 32°F night comes after May 1; 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
- Iowa climateThe statewide normals and every place in the state
- Waukon, IA14 miles from this station, 45.4°F a year
- Decorah, IA19 miles from this station, 48.5°F a year
- Fayette, IA20 miles from this station, 45.0°F a year
- Prairie du Chien, WI22 miles from this station, 47.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made