Rock Rapids, Iowa climate: Normal weather by month, frost dates and records
Rock Rapids's normal year runs from 6°F January nights to 85°F July afternoons, with 29.3 inches of precipitation and 35 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 29°C, 743 mm of precipitation a year.
- NOAA stationRock Rapids
- Station IDUSC00137147
- Location43.43°N 96.17°W
- Elevation1,350 ft (412 m)
- From the centerunder 1 mile
- Population2,709
On October 23, the normal high in Rock Rapids is 57°F and the normal low 33°F, and the chance of measurable rain or snow is 19%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Rock Rapids.
- Jan 25° 6°
- Feb 30° 10°
- Mar 43° 22°
- Apr 58° 34°
- May 70° 47°
- Jun 81° 58°
- Jul 85° 62°
- Aug 82° 59°
- Sep 75° 50°
- Oct 61° 36°
- Nov 44° 23°
- Dec 30° 12°
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 Rock Rapids each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 6°F. The most precipitation falls in June (5.03 in), the least in January (0.61 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 25°F | 6°F | 15.6°F | 0.61 | 6.0 | 5 | <1 | 31 | 9 h 20 min |
| February | 30°F | 10°F | 20.4°F | 0.70 | 7.3 | 5 | <1 | 28 | 10 h 30 min |
| March | 43°F | 22°F | 32.7°F | 1.52 | 5.6 | 6 | <1 | 26 | 11 h 50 min |
| April | 58°F | 34°F | 45.8°F | 3.03 | 3.5 | 9 | <1 | 14 | 13 h 20 min |
| May | 70°F | 47°F | 58.5°F | 3.96 | 0.1 | 12 | 1 | 1 | 14 h 40 min |
| June | 81°F | 58°F | 69.5°F | 5.03 | 0.0 | 11 | 4 | <1 | 15 h 20 min |
| July | 85°F | 62°F | 73.3°F | 3.59 | 0.0 | 8 | 7 | <1 | 15 h 10 min |
| August | 82°F | 59°F | 70.6°F | 3.12 | 0.0 | 9 | 4 | <1 | 14 h |
| September | 75°F | 50°F | 62.4°F | 3.24 | 0.0 | 7 | 2 | 1 | 12 h 30 min |
| October | 61°F | 36°F | 48.6°F | 2.23 | 0.4 | 7 | <1 | 12 | 11 h 10 min |
| November | 44°F | 23°F | 33.6°F | 1.42 | 3.6 | 5 | <1 | 25 | 9 h 40 min |
| December | 30°F | 12°F | 21.2°F | 0.82 | 8.4 | 5 | <1 | 31 | 9 h |
| Year (annual) | 57°F | 35°F | 46.0°F | 29.27 | 34.9 | 86 | 19 | 169 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −4°C | −14°C | −9.1°C | 15 mm | 15 cm |
| February | −1°C | −12°C | −6.4°C | 18 mm | 19 cm |
| March | 6°C | −5°C | 0.4°C | 39 mm | 14 cm |
| April | 14°C | 1°C | 7.7°C | 77 mm | 9 cm |
| May | 21°C | 8°C | 14.7°C | 101 mm | 0 cm |
| June | 27°C | 15°C | 20.8°C | 128 mm | 0 cm |
| July | 29°C | 17°C | 22.9°C | 91 mm | 0 cm |
| August | 28°C | 15°C | 21.4°C | 79 mm | 0 cm |
| September | 24°C | 10°C | 16.9°C | 82 mm | 0 cm |
| October | 16°C | 2°C | 9.2°C | 57 mm | 1 cm |
| November | 7°C | −5°C | 0.9°C | 36 mm | 9 cm |
| December | −1°C | −11°C | −6.0°C | 21 mm | 21 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00137147; 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 Rock Rapids?
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 USC00137147.
When is the last frost in Rock Rapids?
In Rock Rapids, the last spring frost (32°F) comes after May 1 in half of years and after May 13 in one year in ten; the first autumn frost comes before October 4 in half of years and before September 21 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 13; 9 in 10 after April 18
- First autumn frost, half of years before
- October 41 year in 10 before September 21; 9 in 10 before October 19
NOAA puts the median frost-free season at 156 days, and the season without a hard freeze (28°F) at 176 days.
A hard freeze (28°F) comes after April 21 in half of springs and before October 16 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Rock Rapids in zone 5a in ZIP code 51246, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Rock Rapids's NOAA station is in zone 5a: the coldest night of a typical year reaches −19°F (30 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 USC00137147; 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 Rock Rapids?
In a normal year in Rock Rapids, 19 days a year reach 90°F, 169 nights fall to 32°F or colder and 86 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
- 169a normal year
- Days that stay below freezing
- 68high of 32°F or less
- Days with 0.01 inch of precipitation
- 86a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1893) is 111°F, on July 17, 1936; the lowest is −40°F, on January 12, 1912.
The wettest calendar year on that record is 2018, with 45.34 in; the snowiest season is 1961–62, with 79.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00137147; records: ACIS (NOAA Regional Climate Centers), station USC00137147. Records use complete months only; a month missing more than three days is left out.
How sunny is Rock Rapids?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Rock Rapids, 4.1 kWh per square metre a day. July is the sunniest month (85%) and May the cloudiest (71%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 75% | 2.0 |
| February | 79% | 3.1 |
| March | 72% | 3.9 |
| April | 71% | 5.0 |
| May | 71% | 5.6 |
| June | 77% | 6.4 |
| July | 85% | 6.7 |
| August | 81% | 5.5 |
| September | 79% | 4.4 |
| October | 74% | 3.0 |
| November | 74% | 2.1 |
| December | 71% | 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 Rock Rapids need?
A normal year in Rock Rapids brings 7,625 heating degree days, 42% more than the median U.S. place (5,373), and 753 cooling degree days, 17% 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 2,824 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,530 | 0 |
| February | 1,250 | 0 |
| March | 1,000 | 0 |
| April | 578 | 4 |
| May | 244 | 44 |
| June | 37 | 172 |
| July | 7 | 263 |
| August | 18 | 193 |
| September | 148 | 72 |
| October | 513 | 6 |
| November | 942 | 0 |
| December | 1,358 | 0 |
| Year (annual) | 7,625 | 753 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00137147. 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 Rock Rapids been warmer than normal lately?
2025 averaged 47.9°F, 1.9°F above the 1991-2020 normal of 46.0°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 48.2°F | +2.2°F | 27.40 | 25.5 |
| 2022 | 45.3°F | −0.7°F | 20.25 | 21.2 |
| 2023 | 47.4°F | +1.4°F | 22.24 | 41.4 |
| 2024 | 49.1°F | +3.1°F | 37.80 | 19.7 |
| 2025 | 47.9°F | +1.9°F | 25.47 | 34.5 |
Over 101 complete years from 1895 to 2025, the station's annual mean temperature rose at a fitted 3.0°F per century (+0.17°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00137147; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Rock Rapids's climate compare?
Rock Rapids is warmer than 17 of the other 131 places with their own NOAA record in Iowa, and wetter than 3. 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, Rock Rapids 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 Rock Rapids share this climate record?
11 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.
- Luverne, MN4,941 people · 16 mi N
- George, IA1,106 people · 10 mi SE
- Valley Springs, SD872 people · 18 mi NW
- Hills, MN665 people · 12 mi NW
- Ellsworth, MN487 people · 10 mi NE
- Beaver Creek, MN272 people · 16 mi NW
- Lismore, MN202 people · 25 mi NE
- Magnolia, MN188 people · 16 mi N
- Hardwick, MN179 people · 24 mi N
- Steen, MN162 people · 8 mi NW
- Kenneth, MN60 people · 23 mi N
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 Rock Rapids's climate
What is the coldest month in Rock Rapids?
January, with a normal high of 25°F and a normal low of 6°F. The warmest is July (85°F by day, 62°F at night).
Does it snow in Rock Rapids?
Yes: 35 inches in a normal year, falling on 17 days with 0.1 inch or more, the most in December (8.4 inches).
What is the rainiest month in Rock Rapids?
June, with 5.03 in of precipitation in a normal year; the driest is January with 0.61 in.
What plant hardiness zone is Rock Rapids in?
The USDA's 2023 map puts Rock Rapids in zone 5a in ZIP code 51246, the nearest ZIP area. By the same method at Rock Rapids's NOAA station, the coldest night of a typical year reaches −19°F (30 years, 1991-2020): zone 5a.
How late can frost come in Rock Rapids?
In half of years the last 32°F night comes after May 1; in one year in ten it comes after May 13. Waiting until May 13 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Sibley, IA21 miles from this station, 44.5°F a year
- Canton, SD22 miles from this station, 45.7°F a year
- Sheldon, IA24 miles from this station, 44.9°F a year
- Sioux Center, IA26 miles from this station, 48.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made