Photo: Bill Whittaker · CC BY-SA 3.0Hardly any U.S. towns see harsher January nights than Peterson
July afternoons average 84°. By precipitation alone, it ranks drier than 85% of U.S. towns. Decade by decade the climate has edged up, 1.0° above 1901–2000. Garden planting can start around April 30; autumn frost returns near October 5.
A year in Peterson at a glance
Each month’s typical high and low, and what it brings.
What stands out about Peterson’s climate
Compared with towns across the U.S., with Peterson’s place in Iowa beside it.
What a year in Peterson feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 159 frost-free days a year
In half of years the last 32° night comes by April 30 and the first by October 5. Frost and day counts come from NOAA’s station at Sioux Rapids 4 E, IA, 14 miles from the town’s center, 160 ft higher.
The 2023 USDA map puts Peterson’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −18°. 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 35 inches of snow a winter
Snow, measured at Sioux Rapids 4 E, IA, falls mostly in January. Precipitation (rain plus melted snow) adds up to 31 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 96 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Peterson
92% 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 Sioux Rapids 4 E, IA.
Living with Peterson’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
159 frost-free days in zone 5a. The last frost comes by Apr 30 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 5.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 1.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Peterson from natural hazards, river flooding is the largest share (53%); heat waves, cold waves, winter storms and ice storms together are 9%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Peterson and similar climates
TownRatings has no climate map of the towns around Peterson yet.
Climates most like Peterson’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 |
|---|---|---|---|---|
| Peterson, IA | 8° | 84° | 31" | 35" |
| St. Paul, MN | 7° | 83° | 33" | 40" |
| Berlin, WI | 9° | 82° | 33" | 38" |
| Roscoe, IL | 13° | 84° | 37" | 38" |
| Mount Pleasant, MI | 15° | 83° | 33" | 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 Peterson averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.4°).
A smaller shift than in 80% 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 Peterson compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Peterson’s place among Iowa’s.
Peterson weather by month
Highs, lows and precipitation from NOAA’s grid at Peterson’s center; snow, wet days and snow on the ground from Sioux Rapids 4 E, IA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 26° | 8° | 0.7" | 8.0" | 6 | 23 | 6° – 30° |
| February | 31° | 12° | 0.8" | 6.9" | 6 | 20 | 11° – 32° |
| March | 44° | 24° | 1.6" | 6.5" | 7 | 10 | 26° – 50° |
| April | 58° | 35° | 3.4" | 2.3" | 10 | 1 | 36° – 53° |
| May | 70° | 47° | 4.3" | 0.3" | 12 | 0 | 53° – 65° |
| June | 80° | 58° | 4.9" | 0.0" | 11 | 0 | 65° – 74° |
| July | 84° | 62° | 3.5" | 0.0" | 8 | 0 | 66° – 79° |
| August | 81° | 59° | 3.8" | 0.0" | 8 | 0 | 65° – 75° |
| September | 74° | 51° | 3.2" | 0.0" | 8 | 0 | 56° – 67° |
| October | 61° | 38° | 2.3" | 0.7" | 8 | 0 | 43° – 54° |
| November | 44° | 25° | 1.5" | 3.8" | 6 | 6 | 25° – 46° |
| December | 30° | 14° | 1.0" | 6.7" | 6 | 18 | 7° – 29° |
| Year | 57° | 36° | 31.0" | 35.2" | 96 | 77 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 6° to 30°. June is the most reliable, staying within 9°.
Where Peterson’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 Peterson’s center.
- Snow: Sioux Rapids 4 E, IA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Sioux Rapids 4 E, IA, 14 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 Peterson’s climate
What is the weather like in Peterson?
A typical July afternoon reaches 84°, a January night drops to 8°, and about 35 inches of snow falls in a normal winter. Colder January nights than 96% of U.S. towns; cooler July afternoons than 65% of U.S. towns.
How cold does it get in Peterson in winter?
January nights average 8°. About 157 nights a year reach 32° or below and 24 reach 0° or below. In the coldest January of the last 30 years the month averaged 6°.
How much snow does Peterson get?
About 35 inches in a normal winter at Sioux Rapids 4 E, IA, most of it in January, with snow on the ground about 77 days a year.
How hot does it get in Peterson?
July, with a typical high of 84° and a low of 62°. About 11 days a year reach 90° (Sioux Rapids 4 E, IA).
When is the first and last frost in Peterson?
In half of years the last spring frost (32°) comes by April 30 and the first fall frost by October 5, about 159 frost-free days, at Sioux Rapids 4 E, IA.
What growing zone is Peterson in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −18°.
What is the best time of year to visit Peterson?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Peterson getting warmer?
Yes: 1991–2020 averaged 1.0° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 80% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Peterson.
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.