Marshalltown, Iowa climate: Normal weather by month, frost dates and records
Marshalltown's normal year runs from 10°F January nights to 83°F July afternoons, with 32.8 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.7°C, January lows of −12°C, July highs of 28°C, 832 mm of precipitation a year.
- NOAA stationMarshalltown Municipal Airport
- Station IDUSW00094988
- Location42.11°N 92.92°W
- Elevation974 ft (297 m)
- From the center5 miles
- Population27,886
On October 23, the normal high in Marshalltown is 58°F and the normal low 36°F, and the chance of measurable rain or snow is 29%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Marshalltown.
- Jan 28° 10°
- Feb 32° 14°
- Mar 46° 26°
- Apr 60° 37°
- May 71° 49°
- Jun 81° 59°
- Jul 83° 62°
- Aug 81° 60°
- Sep 75° 51°
- Oct 62° 39°
- Nov 46° 26°
- Dec 33° 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 Marshalltown each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 10°F. The most precipitation falls in June (5.32 in), the least in February (0.51 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 28°F | 10°F | 18.9°F | 0.77 | 5 | <1 | 30 | 9 h 30 min |
| February | 32°F | 14°F | 23.2°F | 0.51 | 5 | <1 | 26 | 10 h 30 min |
| March | 46°F | 26°F | 35.7°F | 1.64 | 8 | <1 | 23 | 11 h 50 min |
| April | 60°F | 37°F | 48.3°F | 3.69 | 11 | <1 | 9 | 13 h 20 min |
| May | 71°F | 49°F | 60.0°F | 4.88 | 13 | 1 | 1 | 14 h 30 min |
| June | 81°F | 59°F | 69.7°F | 5.32 | 13 | 3 | <1 | 15 h 10 min |
| July | 83°F | 62°F | 72.6°F | 3.67 | 10 | 5 | <1 | 15 h |
| August | 81°F | 60°F | 70.2°F | 3.88 | 12 | 3 | <1 | 14 h |
| September | 75°F | 51°F | 62.8°F | 3.20 | 10 | 2 | 1 | 12 h 30 min |
| October | 62°F | 39°F | 50.2°F | 2.45 | 10 | <1 | 9 | 11 h 10 min |
| November | 46°F | 26°F | 36.2°F | 1.74 | 7 | <1 | 21 | 9 h 50 min |
| December | 33°F | 16°F | 24.3°F | 1.01 | 6 | <1 | 29 | 9 h 10 min |
| Year (annual) | 58°F | 37°F | 47.7°F | 32.76 | 110 | 12 | 150 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −2°C | −12°C | −7.3°C | 20 mm |
| February | 0°C | −10°C | −4.9°C | 13 mm |
| March | 8°C | −4°C | 2.1°C | 42 mm |
| April | 16°C | 3°C | 9.1°C | 94 mm |
| May | 22°C | 9°C | 15.6°C | 124 mm |
| June | 27°C | 15°C | 20.9°C | 135 mm |
| July | 28°C | 17°C | 22.6°C | 93 mm |
| August | 27°C | 15°C | 21.2°C | 99 mm |
| September | 24°C | 10°C | 17.1°C | 81 mm |
| October | 17°C | 4°C | 10.1°C | 62 mm |
| November | 8°C | −3°C | 2.3°C | 44 mm |
| December | 1°C | −9°C | −4.3°C | 26 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. Marshalltown's own co-op station Marshalltown station does: 25 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094988; 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 Marshalltown?
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 (10).
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 USW00094988.
When is the last frost in Marshalltown?
In Marshalltown, the last spring frost (32°F) comes after April 30 in half of years and after May 12 in one year in ten; the first autumn frost comes before October 6 in half of years and before September 22 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 301 year in 10 after May 12; 9 in 10 after April 15
- First autumn frost, half of years before
- October 61 year in 10 before September 22; 9 in 10 before October 19
NOAA puts the median frost-free season at 159 days, and the season without a hard freeze (28°F) at 179 days.
A hard freeze (28°F) comes after April 19 in half of springs and before October 16 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Marshalltown in zone 5a in ZIP code 50158, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Marshalltown's NOAA station is in zone 5a: the coldest night of a typical year reaches −17°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 USW00094988; 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 Marshalltown?
In a normal year in Marshalltown, 12 days a year reach 90°F, 150 nights fall to 32°F or colder and 110 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
- 150a normal year
- Days that stay below freezing
- 58high of 32°F or less
- Days with 0.01 inch of precipitation
- 110a normal year
The highest temperature in this station's record (since 1996) is 102°F, on July 25, 2012; the lowest is −28°F, on January 16, 2009.
The wettest calendar year on that record is 2015, with 44.62 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00094988; records: ACIS (NOAA Regional Climate Centers), station USW00094988. Records use complete months only; a month missing more than three days is left out.
How sunny is Marshalltown?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Marshalltown, 4.0 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 | 70% | 1.9 |
| February | 76% | 3.0 |
| March | 72% | 3.9 |
| April | 69% | 4.8 |
| May | 71% | 5.6 |
| June | 76% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 79% | 4.4 |
| October | 71% | 3.0 |
| November | 70% | 2.0 |
| 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 Marshalltown need?
A normal year in Marshalltown brings 6,996 heating degree days, 30% more than the median U.S. place (5,373), and 727 cooling degree days, 20% 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 2,900 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,429 | 0 |
| February | 1,170 | 0 |
| March | 908 | 1 |
| April | 506 | 4 |
| May | 205 | 49 |
| June | 26 | 169 |
| July | 7 | 244 |
| August | 17 | 180 |
| September | 135 | 71 |
| October | 467 | 10 |
| November | 864 | 0 |
| December | 1,260 | 0 |
| Year (annual) | 6,996 | 727 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094988. 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 Marshalltown been warmer than normal lately?
2025 averaged 49.3°F, 1.6°F above the 1991-2020 normal of 47.7°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 49.2°F | +1.5°F | – |
| 2022 | 47.1°F | −0.6°F | – |
| 2023 | 51.0°F | +3.3°F | – |
| 2024 | 52.0°F | +4.3°F | – |
| 2025 | 49.3°F | +1.6°F | 35.14 |
Source: observed years: ACIS, station USW00094988. A year counts only with all twelve months complete.
How does Marshalltown's climate compare?
Marshalltown is warmer than 59 of the other 131 places with their own NOAA record in Iowa, and wetter than 20. Across the 7,247 U.S. stations with normals, its annual mean of 47.7°F is warmer than 31%.
In the Köppen classification computed from these normals, Marshalltown is Dwa: continental, dry-winter, 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 Marshalltown share this climate record?
8 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.
- Conrad, IA1,098 people · 8 mi N
- Gladbrook, IA775 people · 12 mi NE
- Albion, IA444 people · 4 mi W
- Liscomb, IA292 people · 7 mi NW
- Haverhill, IA164 people · 12 mi S
- Beaman, IA155 people · 9 mi NE
- Green Mountain, IA105 people · 5 mi E
- Ferguson, IA98 people · 12 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.
What do Marshalltown's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Marshalltown. This page uses Marshalltown Municipal Airport; the other differs by site and elevation:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Marshalltown station USC00135198 | 2 mi NW | 870 ft | 47.6°F | 9°F | 84°F | 37.9 | 25 | April 28 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Marshalltown's climate
What is the coldest month in Marshalltown?
January, with a normal high of 28°F and a normal low of 10°F. The warmest is July (83°F by day, 62°F at night).
Does it snow in Marshalltown?
Yes. NOAA publishes no 1991-2020 snowfall normal for Marshalltown's NOAA station; Marshalltown's own co-op station Marshalltown station records 25 inches of snow in a normal year.
What is the rainiest month in Marshalltown?
June, with 5.32 in of precipitation in a normal year; the driest is February with 0.51 in.
What plant hardiness zone is Marshalltown in?
The USDA's 2023 map puts Marshalltown in zone 5a in ZIP code 50158, the nearest ZIP area. By the same method at Marshalltown's NOAA station, the coldest night of a typical year reaches −17°F (23 years, 1991-2020): zone 5a.
How late can frost come in Marshalltown?
In half of years the last 32°F night comes after April 30; in one year in ten it comes after May 12. Waiting until May 12 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Marshalltown in OctoberThis month day by day, its records and recent years
- Iowa climateThe statewide normals and every place in the state
- Toledo, IA18 miles from this station, 47.3°F a year
- Grundy Center, IA19 miles from this station, 47.1°F a year
- Eldora, IA20 miles from this station, 46.9°F a year
- Colo, IA22 miles from this station, 47.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made