Sioux City, Iowa climate: Normal weather by month, frost dates and records
Sioux City's normal year runs from 10°F January nights to 85°F July afternoons, with 29.3 inches of precipitation and 36 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.2°C, January lows of −12°C, July highs of 29°C, 743 mm of precipitation a year.
- NOAA stationSioux City Airport
- Station IDUSW00014943
- Location42.39°N 96.38°W
- Elevation1,095 ft (334 m)
- From the center7 miles
- Population86,875
On October 14, the normal high in Sioux City is 64°F and the normal low 39°F, and the chance of measurable rain or snow is 24%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Sioux City.
- Jan 30° 10°
- Feb 34° 15°
- Mar 48° 26°
- Apr 61° 37°
- May 72° 49°
- Jun 82° 59°
- Jul 85° 63°
- Aug 83° 61°
- Sep 77° 51°
- Oct 63° 38°
- Nov 47° 25°
- Dec 33° 15°
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 Sioux City each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 10°F. The most precipitation falls in June (4.35 in), the least in January (0.69 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. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 30°F | 10°F | 20.0°F | 0.69 | 7.7 | 7 | <1 | 31 | 9 h 20 min |
| February | 34°F | 15°F | 24.5°F | 0.86 | 8.7 | 7 | <1 | 27 | 10 h 30 min |
| March | 48°F | 26°F | 36.7°F | 1.76 | 5.7 | 8 | <1 | 23 | 11 h 50 min |
| April | 61°F | 37°F | 48.9°F | 3.15 | 2.3 | 10 | <1 | 10 | 13 h 20 min |
| May | 72°F | 49°F | 60.5°F | 3.87 | 0.0 | 12 | 2 | 1 | 14 h 30 min |
| June | 82°F | 59°F | 70.7°F | 4.35 | 0.0 | 12 | 6 | <1 | 15 h 20 min |
| July | 85°F | 63°F | 74.2°F | 3.35 | 0.0 | 9 | 8 | <1 | 15 h |
| August | 83°F | 61°F | 71.7°F | 3.94 | 0.0 | 10 | 5 | <1 | 14 h |
| September | 77°F | 51°F | 63.9°F | 2.84 | 0.0 | 8 | 2 | 1 | 12 h 30 min |
| October | 63°F | 38°F | 50.3°F | 2.20 | 0.8 | 8 | 1 | 9 | 11 h 10 min |
| November | 47°F | 25°F | 35.9°F | 1.27 | 3.2 | 6 | <1 | 23 | 9 h 50 min |
| December | 33°F | 15°F | 24.1°F | 0.99 | 7.6 | 7 | <1 | 30 | 9 h 10 min |
| Year (annual) | 60°F | 37°F | 48.5°F | 29.27 | 36.0 | 102 | 25 | 154 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −12°C | −6.7°C | 18 mm | 20 cm |
| February | 1°C | −10°C | −4.2°C | 22 mm | 22 cm |
| March | 9°C | −3°C | 2.6°C | 45 mm | 14 cm |
| April | 16°C | 3°C | 9.4°C | 80 mm | 6 cm |
| May | 22°C | 9°C | 15.8°C | 98 mm | 0 cm |
| June | 28°C | 15°C | 21.5°C | 110 mm | 0 cm |
| July | 29°C | 17°C | 23.4°C | 85 mm | 0 cm |
| August | 28°C | 16°C | 22.1°C | 100 mm | 0 cm |
| September | 25°C | 11°C | 17.7°C | 72 mm | 0 cm |
| October | 17°C | 3°C | 10.2°C | 56 mm | 2 cm |
| November | 8°C | −4°C | 2.2°C | 32 mm | 8 cm |
| December | 1°C | −10°C | −4.4°C | 25 mm | 19 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014943; 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 Sioux City?
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 (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 USW00014943.
When is the last frost in Sioux City?
In Sioux City, the last spring frost (32°F) comes after April 29 in half of years and after May 14 in one year in ten; the first autumn frost comes before October 5 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 291 year in 10 after May 14; 9 in 10 after April 16
- First autumn frost, half of years before
- October 51 year in 10 before September 22; 9 in 10 before October 18
NOAA puts the median frost-free season at 159 days, and the season without a hard freeze (28°F) at 177 days.
A hard freeze (28°F) comes after April 20 in half of springs and before October 15 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Sioux City in zone 5a across its 8 ZIP code areas (5a in 51106, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Sioux City's NOAA station is in zone 5a: the coldest night of a typical year reaches −16°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 USW00014943; 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.
What hardiness zone is each Sioux City ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Sioux City's 8 ZIP code areas are all in zone 5a. Each ZIP's frost dates are in the frost tool.
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in Sioux City?
In a normal year in Sioux City, 25 days a year reach 90°F (1 of them 100°F or more), 154 nights fall to 32°F or colder and 102 days bring measurable precipitation.
- Days at 90°F or more
- 25a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 154a normal year
- Days that stay below freezing
- 51high of 32°F or less
- Days with 0.01 inch of precipitation
- 102a normal year
- Days with 1 inch of snow or more
- 11a normal year
The highest temperature in Sioux City's official record (kept by the National Weather Service since 1889) is 111°F, on July 17, 1936; the lowest is −35°F, on January 12, 1912.
The wettest calendar year on that record is 2014, with 41.36 in; the snowiest season is 1916–17, with 72.8 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00014943; records: ACIS (NOAA Regional Climate Centers), NWS threaded record SUXthr. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Sioux City, and how clear are its skies?
The summer (June-August) dew point averages 63°F. The muggiest month is July, with an average dew point of 64°F; the driest air comes in December (15°F). March is the windiest month (12.3 mph on average), and August has the most clear or nearly clear hours (77%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 16°F | 75% | 64% | 10.6 mph | 55% | 35% |
| February | 20°F | 72% | 57% | 11.3 mph | 55% | 34% |
| March | 31°F | 63% | 43% | 12.3 mph | 56% | 32% |
| April | 41°F | 61% | 43% | 11.7 mph | 57% | 30% |
| May | 54°F | 65% | 47% | 10.0 mph | 62% | 24% |
| June | 63°F | 70% | 52% | 8.8 mph | 75% | 11% |
| July | 64°F | 74% | 55% | 7.6 mph | 73% | 13% |
| August | 61°F | 74% | 53% | 8.1 mph | 77% | 13% |
| September | 46°F | 66% | 42% | 9.3 mph | 73% | 18% |
| October | 32°F | 67% | 46% | 10.5 mph | 65% | 26% |
| November | 22°F | 74% | 59% | 10.6 mph | 61% | 31% |
| December | 15°F | 77% | 66% | 10.7 mph | 58% | 34% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014943. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Sioux City?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Sioux City, 4.2 kWh per square metre a day. July is the sunniest month (84%) and December the cloudiest (69%). Among the 459 U.S. places of 50,000 or more, that ranks tied 276th (with 27 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 72% | 2.0 |
| February | 77% | 3.1 |
| March | 70% | 3.8 |
| April | 71% | 5.0 |
| May | 72% | 5.8 |
| June | 79% | 6.5 |
| July | 84% | 6.6 |
| August | 81% | 5.6 |
| September | 80% | 4.5 |
| October | 75% | 3.1 |
| November | 75% | 2.2 |
| December | 69% | 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 Sioux City need?
A normal year in Sioux City brings 6,860 heating degree days, 28% more than the median U.S. place (5,373), and 866 cooling degree days, 5% 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 3,077 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,396 | 0 |
| February | 1,134 | 0 |
| March | 877 | 1 |
| April | 490 | 7 |
| May | 197 | 57 |
| June | 26 | 195 |
| July | 4 | 289 |
| August | 11 | 219 |
| September | 121 | 88 |
| October | 464 | 9 |
| November | 873 | 0 |
| December | 1,268 | 0 |
| Year (annual) | 6,860 | 866 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014943. 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 Sioux City been warmer than normal lately?
2025 averaged 50.1°F, 1.6°F above the 1991-2020 normal of 48.5°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 50.5°F | +2.0°F | 22.96 | 25.5 |
| 2022 | 49.0°F | +0.5°F | 15.34 | 10.9 |
| 2023 | 50.8°F | +2.3°F | 27.60 | 31.1 |
| 2024 | 51.5°F | +3.0°F | 32.27 | 30.3 |
| 2025 | 50.1°F | +1.6°F | 27.53 | 32.7 |
Over 83 complete years from 1941 to 2025, the station's annual mean temperature rose at a fitted 2.7°F per century (+0.15°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00014943; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Sioux City's climate compare?
Sioux City is warmer than 76 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 48.5°F is warmer than 34%.
In the Köppen classification computed from these normals, Sioux City 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 Sioux City share this climate record?
3 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.
- Winnebago, NE892 people · 12 mi SW
- Homer, NE517 people · 7 mi SW
- Hubbard, NE172 people · 11 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.
What do Sioux City's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Sioux City. This page uses Sioux City Airport; the other differs by site and elevation, and the linked ones have pages of their own:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Sioux City Ang USC00137702 | 7 mi S | 1,100 ft | 48.0°F | 9°F | 86°F | 30.3 | – | April 29 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Sioux City's climate
What is the coldest month in Sioux City?
January, with a normal high of 30°F and a normal low of 10°F. The warmest is July (85°F by day, 63°F at night).
Does it snow in Sioux City?
Yes: 36 inches in a normal year, falling on 25 days with 0.1 inch or more, the most in February (8.7 inches).
What is the rainiest month in Sioux City?
June, with 4.35 in of precipitation in a normal year; the driest is January with 0.69 in.
What plant hardiness zone is Sioux City in?
The USDA's 2023 map puts Sioux City in zone 5a across its 8 ZIP code areas (5a in 51106, the largest). By the same method at Sioux City's NOAA station, the coldest night of a typical year reaches −16°F (30 years, 1991-2020): zone 5a.
How late can frost come in Sioux City?
In half of years the last 32°F night comes after April 29; 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
- Sioux City in OctoberThis month day by day, its records and recent years
- Iowa climateThe statewide normals and every place in the state
- Sioux City Ang, IA1 miles from this station, 48.0°F a year
- Walthill, NE17 miles from this station, 49.0°F a year
- Onawa, IA25 miles from this station, 48.5°F a year
- Wakefield, NE26 miles from this station, 48.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made