Jefferson, Iowa climate: Normal weather by month, frost dates and records
Jefferson's normal year runs from 9°F January nights to 83°F July afternoons, with 35.3 inches of precipitation and 32 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.8°C, January lows of −13°C, July highs of 29°C, 897 mm of precipitation a year.
- NOAA stationJefferson
- Station IDUSC00134228
- Location42.01°N 94.40°W
- Elevation1,055 ft (322 m)
- From the center1 miles
- Population4,148
On October 24, the normal high in Jefferson is 59°F and the normal low 36°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 Jefferson.
- Jan 28° 9°
- Feb 33° 13°
- Mar 46° 25°
- Apr 60° 36°
- May 71° 49°
- Jun 81° 59°
- Jul 83° 63°
- Aug 81° 60°
- Sep 76° 51°
- Oct 63° 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 Jefferson each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 9°F. The most precipitation falls in June (5.19 in), the least in January (0.96 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 28°F | 9°F | 18.4°F | 0.96 | 8.2 | 7 | <1 | 31 | 9 h 30 min |
| February | 33°F | 13°F | 22.9°F | 1.28 | 8.2 | 7 | <1 | 26 | 10 h 30 min |
| March | 46°F | 25°F | 35.6°F | 1.96 | 4.8 | 8 | <1 | 23 | 11 h 50 min |
| April | 60°F | 36°F | 48.1°F | 3.58 | 0.9 | 10 | <1 | 9 | 13 h 20 min |
| May | 71°F | 49°F | 59.9°F | 4.97 | 0.0 | 12 | 1 | 1 | 14 h 30 min |
| June | 81°F | 59°F | 69.9°F | 5.19 | 0.0 | 12 | 3 | <1 | 15 h 10 min |
| July | 83°F | 63°F | 73.1°F | 4.38 | 0.0 | 10 | 8 | <1 | 15 h |
| August | 81°F | 60°F | 70.9°F | 4.21 | 0.0 | 9 | 5 | <1 | 14 h |
| September | 76°F | 51°F | 63.5°F | 3.13 | 0.0 | 8 | 2 | <1 | 12 h 30 min |
| October | 63°F | 39°F | 51.0°F | 2.58 | 0.6 | 8 | <1 | 8 | 11 h 10 min |
| November | 46°F | 26°F | 36.1°F | 1.69 | 1.5 | 6 | <1 | 21 | 9 h 50 min |
| December | 33°F | 16°F | 24.2°F | 1.38 | 7.5 | 7 | <1 | 30 | 9 h 10 min |
| Year (annual) | 58°F | 37°F | 47.8°F | 35.31 | 31.7 | 102 | 19 | 149 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −2°C | −13°C | −7.6°C | 24 mm | 21 cm |
| February | 0°C | −10°C | −5.1°C | 33 mm | 21 cm |
| March | 8°C | −4°C | 2.0°C | 50 mm | 12 cm |
| April | 16°C | 2°C | 8.9°C | 91 mm | 2 cm |
| May | 22°C | 9°C | 15.5°C | 126 mm | 0 cm |
| June | 27°C | 15°C | 21.1°C | 132 mm | 0 cm |
| July | 29°C | 17°C | 22.8°C | 111 mm | 0 cm |
| August | 27°C | 16°C | 21.6°C | 107 mm | 0 cm |
| September | 24°C | 11°C | 17.5°C | 80 mm | 0 cm |
| October | 17°C | 4°C | 10.6°C | 66 mm | 2 cm |
| November | 8°C | −4°C | 2.3°C | 43 mm | 4 cm |
| December | 0°C | −9°C | −4.3°C | 35 mm | 19 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00134228; 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 Jefferson?
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 USC00134228.
When is the last frost in Jefferson?
In Jefferson, the last spring frost (32°F) comes after April 26 in half of years and after May 8 in one year in ten; the first autumn frost comes before October 9 in half of years and before September 23 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 261 year in 10 after May 8; 9 in 10 after April 12
- First autumn frost, half of years before
- October 91 year in 10 before September 23; 9 in 10 before October 24
NOAA puts the median frost-free season at 164 days, and the season without a hard freeze (28°F) at 185 days.
A hard freeze (28°F) comes after April 15 in half of springs and before October 21 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Jefferson in zone 5b in ZIP code 50129, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Jefferson's NOAA station is in zone 5b: the coldest night of a typical year reaches −14°F (25 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 USC00134228; 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 Jefferson?
In a normal year in Jefferson, 19 days a year reach 90°F (1 of them 100°F or more), 149 nights fall to 32°F or colder and 102 days bring measurable precipitation.
- Days at 90°F or more
- 19a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 149a normal year
- Days that stay below freezing
- 55high of 32°F or less
- Days with 0.01 inch of precipitation
- 102a normal year
- Days with 1 inch of snow or more
- 10a normal year
The highest temperature in this station's record (since 1893) is 111°F, on July 5, 1911; the lowest is −37°F, on January 12, 1912.
The wettest calendar year on that record is 1973, with 49.71 in; the snowiest season is 1961–62, with 68.8 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00134228; records: ACIS (NOAA Regional Climate Centers), station USC00134228. Records use complete months only; a month missing more than three days is left out.
How sunny is Jefferson?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Jefferson, 4.1 kWh per square metre a day. July is the sunniest month (82%) and December the cloudiest (68%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 71% | 2.0 |
| February | 75% | 3.0 |
| March | 70% | 3.8 |
| April | 70% | 4.8 |
| May | 71% | 5.6 |
| June | 76% | 6.3 |
| July | 82% | 6.5 |
| August | 80% | 5.5 |
| September | 79% | 4.4 |
| October | 73% | 3.1 |
| November | 72% | 2.1 |
| December | 68% | 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 Jefferson need?
A normal year in Jefferson brings 7,002 heating degree days, 30% more than the median U.S. place (5,373), and 768 cooling degree days, 15% 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 2,966 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,446 | 0 |
| February | 1,179 | 0 |
| March | 911 | 1 |
| April | 512 | 5 |
| May | 205 | 47 |
| June | 27 | 174 |
| July | 6 | 257 |
| August | 15 | 196 |
| September | 124 | 77 |
| October | 445 | 11 |
| November | 869 | 0 |
| December | 1,265 | 0 |
| Year (annual) | 7,002 | 768 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00134228. 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 Jefferson been warmer than normal lately?
2023 averaged 49.9°F, 2.1°F above the 1991-2020 normal of 47.8°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 49.9°F | +2.1°F | 29.28 | 31.7 |
| 2022 | 47.0°F | −0.8°F | 28.86 | 29.4 |
| 2023 | 49.9°F | +2.1°F | 29.23 | – |
Over 93 complete years from 1911 to 2023, the station's annual mean temperature rose at a fitted 0.6°F per century (+0.03°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00134228; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Jefferson's climate compare?
Jefferson is warmer than 60 of the other 131 places with their own NOAA record in Iowa, and wetter than 44. Across the 7,247 U.S. stations with normals, its annual mean of 47.8°F is warmer than 31%.
In the Köppen classification computed from these normals, Jefferson 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 Jefferson share this climate record?
7 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.
- Grand Junction, IA715 people · 8 mi E
- Scranton, IA496 people · 8 mi W
- Churdan, IA359 people · 11 mi NW
- Harcourt, IA257 people · 21 mi NE
- Bagley, IA230 people · 11 mi S
- Paton, IA217 people · 13 mi NE
- Dana, IA34 people · 11 mi NE
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 Jefferson's climate
What is the coldest month in Jefferson?
January, with a normal high of 28°F and a normal low of 9°F. The warmest is July (83°F by day, 63°F at night).
Does it snow in Jefferson?
Yes: 32 inches in a normal year, falling on 21 days with 0.1 inch or more, the most in January (8.2 inches).
What is the rainiest month in Jefferson?
June, with 5.19 in of precipitation in a normal year; the driest is January with 0.96 in.
What plant hardiness zone is Jefferson in?
The USDA's 2023 map puts Jefferson in zone 5b in ZIP code 50129, the nearest ZIP area. By the same method at Jefferson's NOAA station, the coldest night of a typical year reaches −14°F (25 years, 1991-2020): zone 5b.
How late can frost come in Jefferson?
In half of years the last 32°F night comes after April 26; in one year in ten it comes after May 8. Waiting until May 8 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Perry, IA19 miles from this station, 48.9°F a year
- Carroll, IA24 miles from this station, 48.3°F a year
- Guthrie Center, IA24 miles from this station, 48.4°F a year
- Boone, IA26 miles from this station, 48.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made