Photo: PopePompus · CC BY-SA 4.0January in Swan bites harder than in 89% of U.S. towns
On a normal July day the thermometer tops out near 86°. By precipitation alone, it ranks drier than 74% of U.S. towns. December has warmed most since 1901–2000, part of a 0.5° rise. Plan time outside from May to June and August to October, when highs sit at 64–84°.
A year in Swan at a glance
Each month’s typical high and low, and what it brings.
What stands out about Swan’s climate
Compared with towns across the U.S., with Swan’s place in Iowa beside it.
What a year in Swan feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 174 frost-free days a year
In half of years the last 32° night comes by April 21 and the first by October 15. Frost and day counts come from NOAA’s station at Des Moines 17 E, IA, 6 miles from the town’s center, 160 ft higher.
The 2023 USDA map puts Swan’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −12°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 37 inches of snow a winter
Snow, measured at Des Moines International Airport, is heaviest from January through February, about 10 inches a month. Precipitation (rain plus melted snow) adds up to 36 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 113 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Swan
89% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Des Moines 17 E, IA.
Living with Swan’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
174 frost-free days in zone 5b. The last frost comes by Apr 21 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 15.
Months with highs of 62–84° and lows of 40° or more: May, June, August, September and October. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Swan from natural hazards, river flooding is the largest share (37%); heat waves, cold waves, winter storms and ice storms together are 13%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Swan and similar climates
TownRatings has no climate map of the towns around Swan yet.
Climates most like Swan’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Swan, IA | 13° | 86° | 36" | 37" |
| Silvis, IL | 15° | 85° | 37" | 36" |
| Gretna, NE | 15° | 86° | 33" | 36" |
| Beloit, WI | 13° | 83° | 37" | 37" |
| Milan, MI | 17° | 84° | 34" | 39" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Swan averaged 0.5° warmer than the 1900s. The biggest change is in December (+2.0°).
A smaller shift than in 98% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Swan compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Swan’s place among Iowa’s.
Swan weather by month
Highs, lows and precipitation from NOAA’s grid at Swan’s center; snow, wet days and snow on the ground from Des Moines International Airport. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 31° | 13° | 0.9" | 9.4" | 8 | 18 | 13° – 35° |
| February | 36° | 17° | 1.2" | 10.2" | 8 | 15 | 16° – 38° |
| March | 49° | 29° | 2.0" | 4.4" | 10 | 5 | 31° – 54° |
| April | 62° | 40° | 3.8" | 1.2" | 12 | 1 | 42° – 58° |
| May | 72° | 51° | 5.0" | 0.2" | 13 | 0 | 56° – 69° |
| June | 82° | 61° | 5.4" | 0.0" | 12 | 0 | 68° – 75° |
| July | 86° | 65° | 4.1" | 0.0" | 10 | 0 | 70° – 82° |
| August | 84° | 62° | 4.2" | 0.0" | 9 | 0 | 68° – 78° |
| September | 77° | 54° | 3.5" | 0.0" | 8 | 0 | 59° – 70° |
| October | 64° | 41° | 2.7" | 0.5" | 9 | 0 | 47° – 58° |
| November | 49° | 30° | 1.9" | 2.7" | 8 | 2 | 31° – 50° |
| December | 36° | 19° | 1.3" | 7.9" | 8 | 10 | 12° – 35° |
| Year | 61° | 40° | 35.9" | 36.5" | 113 | 52 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 12° to 35°. June is the most reliable, staying within 7°.
Where Swan’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Swan’s center.
- Snow: Des Moines International Airport.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Des Moines 17 E, IA, 6 miles from the town’s center, 160 ft higher; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Swan’s climate
What is the weather like in Swan?
A typical July afternoon reaches 86°, a January night drops to 13°, and about 37 inches of snow falls in a normal winter. Colder January nights than 89% of U.S. towns; hotter July afternoons than 52% of U.S. towns.
How cold does it get in Swan in winter?
January nights average 13°. About 137 nights a year reach 32° or below and 15 reach 0° or below. In the coldest January of the last 30 years the month averaged 13°.
How much snow does Swan get?
About 37 inches in a normal winter at Des Moines International Airport, heaviest from January through February, about 10 inches a month, with snow on the ground about 52 days a year.
How hot does it get in Swan?
July, with a typical high of 86° and a low of 65°. About 14 days a year reach 90° (Des Moines 17 E, IA).
When is the first and last frost in Swan?
In half of years the last spring frost (32°) comes by April 21 and the first fall frost by October 15, about 174 frost-free days, at Des Moines 17 E, IA.
What growing zone is Swan in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −12°.
What is the best time of year to visit Swan?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Swan getting warmer?
Yes: 1991–2020 averaged 0.5° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 98% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Swan.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.