Swea City, Iowa climate: Normal weather by month, frost dates and records
Swea City's normal year runs from 5°F January nights to 81°F July afternoons, with 32.9 inches of precipitation and 40 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.6°C, January lows of −15°C, July highs of 27°C, 835 mm of precipitation a year.
- NOAA stationSwea City (5 mi N)
- Station IDUSC00138026
- Location43.45°N 94.31°W
- Elevation1,180 ft (360 m)
- From the center5 miles
- Population545
On October 23, the normal high in Swea City is 55°F and the normal low 32°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Swea City.
- Jan 22° 5°
- Feb 27° 8°
- Mar 40° 21°
- Apr 55° 33°
- May 68° 46°
- Jun 78° 57°
- Jul 81° 60°
- Aug 78° 58°
- Sep 73° 48°
- Oct 59° 35°
- Nov 42° 22°
- Dec 28° 11°
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 Swea City each month?
July is the warmest month, with normal highs of 81°F; January the coldest, with normal lows of 5°F. The most precipitation falls in June (4.65 in), the least in January (0.87 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 22°F | 5°F | 13.2°F | 0.87 | 10.9 | 6 | <1 | 31 | 9 h 20 min |
| February | 27°F | 8°F | 17.5°F | 0.93 | 8.5 | 5 | <1 | 27 | 10 h 30 min |
| March | 40°F | 21°F | 30.5°F | 1.76 | 4.6 | 7 | <1 | 26 | 11 h 50 min |
| April | 55°F | 33°F | 43.9°F | 3.43 | 3.6 | 10 | <1 | 12 | 13 h 20 min |
| May | 68°F | 46°F | 56.6°F | 4.60 | 0.0 | 12 | 1 | 1 | 14 h 40 min |
| June | 78°F | 57°F | 67.3°F | 4.65 | 0.0 | 11 | 3 | <1 | 15 h 20 min |
| July | 81°F | 60°F | 70.3°F | 4.16 | 0.0 | 9 | 5 | <1 | 15 h 10 min |
| August | 78°F | 58°F | 67.9°F | 4.11 | 0.0 | 8 | 2 | <1 | 14 h |
| September | 73°F | 48°F | 60.3°F | 3.21 | 0.0 | 8 | 1 | 1 | 12 h 30 min |
| October | 59°F | 35°F | 46.9°F | 2.52 | 0.7 | 7 | <1 | 11 | 11 h 10 min |
| November | 42°F | 22°F | 32.0°F | 1.46 | 3.1 | 6 | <1 | 24 | 9 h 40 min |
| December | 28°F | 11°F | 19.4°F | 1.17 | 8.3 | 6 | <1 | 31 | 9 h |
| Year (annual) | 54°F | 34°F | 43.8°F | 32.87 | 39.7 | 93 | 11 | 163 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −6°C | −15°C | −10.4°C | 22 mm | 28 cm |
| February | −3°C | −13°C | −8.1°C | 24 mm | 22 cm |
| March | 4°C | −6°C | −0.8°C | 45 mm | 12 cm |
| April | 13°C | 0°C | 6.6°C | 87 mm | 9 cm |
| May | 20°C | 8°C | 13.7°C | 117 mm | 0 cm |
| June | 25°C | 14°C | 19.6°C | 118 mm | 0 cm |
| July | 27°C | 15°C | 21.3°C | 106 mm | 0 cm |
| August | 26°C | 14°C | 19.9°C | 104 mm | 0 cm |
| September | 23°C | 9°C | 15.7°C | 82 mm | 0 cm |
| October | 15°C | 2°C | 8.3°C | 64 mm | 2 cm |
| November | 5°C | −5°C | 0.0°C | 37 mm | 8 cm |
| December | −2°C | −12°C | −7.0°C | 30 mm | 21 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00138026; 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 Swea City?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, August has the fewest days with rain (8).
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 USC00138026.
When is the last frost in Swea City?
In Swea City, the last spring frost (32°F) comes after May 4 in half of years and after May 14 in one year in ten; the first autumn frost comes before October 1 in half of years and before September 18 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 41 year in 10 after May 14; 9 in 10 after April 21
- First autumn frost, half of years before
- October 11 year in 10 before September 18; 9 in 10 before October 15
NOAA puts the median frost-free season at 150 days, and the season without a hard freeze (28°F) at 168 days.
A hard freeze (28°F) comes after April 25 in half of springs and before October 10 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Swea City in zone 5a in ZIP code 50590, 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 USC00138026; 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 Swea City?
In a normal year in Swea City, 11 days a year reach 90°F, 163 nights fall to 32°F or colder and 93 days bring measurable precipitation.
- Days at 90°F or more
- 11a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 163a normal year
- Days that stay below freezing
- 73high of 32°F or less
- Days with 0.01 inch of precipitation
- 93a normal year
- Days with 1 inch of snow or more
- 14a normal year
The highest temperature in this station's record (since 1954) is 105°F, on June 8, 1985; the lowest is −32°F, on January 21, 1970.
The wettest calendar year on that record is 1993, with 47.02 in; the snowiest season is 2018–19, with 91.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00138026; records: ACIS (NOAA Regional Climate Centers), station USC00138026. Records use complete months only; a month missing more than three days is left out.
How sunny is Swea City?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Swea City, 4.0 kWh per square metre a day. July is the sunniest month (83%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 71% | 1.9 |
| February | 77% | 3.0 |
| March | 71% | 3.8 |
| April | 69% | 4.8 |
| May | 70% | 5.5 |
| June | 75% | 6.2 |
| July | 83% | 6.5 |
| August | 80% | 5.5 |
| September | 78% | 4.3 |
| October | 72% | 2.9 |
| November | 70% | 2.0 |
| December | 66% | 1.5 |
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 Swea City need?
A normal year in Swea City brings 8,171 heating degree days, 52% more than the median U.S. place (5,373), and 497 cooling degree days, 45% 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 2,421 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,606 | 0 |
| February | 1,330 | 0 |
| March | 1,068 | 0 |
| April | 633 | 2 |
| May | 287 | 28 |
| June | 50 | 120 |
| July | 14 | 178 |
| August | 34 | 123 |
| September | 183 | 42 |
| October | 564 | 4 |
| November | 990 | 0 |
| December | 1,414 | 0 |
| Year (annual) | 8,171 | 497 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00138026. 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 Swea City been warmer than normal lately?
2022 averaged 43.0°F, 0.8°F below the 1991-2020 normal of 43.8°F.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2022 | 43.0°F | −0.8°F | 22.99 | 45.4 |
Over 33 complete years from 1957 to 2022, the station's annual mean temperature rose at a fitted 0.2°F per century (+0.01°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00138026; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Swea City's climate compare?
Swea City is warmer than 1 of the other 131 places with their own NOAA record in Iowa, and wetter than 22. Across the 7,247 U.S. stations with normals, its annual mean of 43.8°F is warmer than 15%.
In the Köppen classification computed from these normals, Swea City is Dfb: continental, no dry season, warm 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 Swea City share this climate record?
6 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.
- Blue Earth, MN3,159 people · 17 mi NE
- Bancroft, IA677 people · 12 mi S
- Elmore, MN545 people · 12 mi E
- Lakota, IA261 people · 12 mi SE
- Frost, MN214 people · 21 mi NE
- Ledyard, IA118 people · 8 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 Swea City's climate
What is the coldest month in Swea City?
January, with a normal high of 22°F and a normal low of 5°F. The warmest is July (81°F by day, 60°F at night).
Does it snow in Swea City?
Yes: 40 inches in a normal year, falling on 23 days with 0.1 inch or more, the most in January (10.9 inches).
What is the rainiest month in Swea City?
June, with 4.65 in of precipitation in a normal year; the driest is January with 0.87 in.
What plant hardiness zone is Swea City in?
The USDA's 2023 map puts Swea City in zone 5a in ZIP code 50590, the nearest ZIP area.
How late can frost come in Swea City?
In half of years the last 32°F night comes after May 4; 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
- Fairmont, MN16 miles from this station, 46.1°F a year
- Estherville, IA22 miles from this station, 44.6°F a year
- Winnebago, MN22 miles from this station, 45.6°F a year
- Sherburn, MN26 miles from this station, 45.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made