January in Iona Township bites harder than in 92% of U.S. towns
July afternoons average 88°. It is a dry place: less rain and snow fall here than on 88% of U.S. towns. The latest 30-year average runs 1.3° warmer than 1901–2000’s, with January up the most. For walks and days out, May, June and September bring highs of 71–81°.
A year in Iona Township at a glance
Each month’s typical high and low, and what it brings.
What stands out about Iona Township’s climate
Compared with towns across the U.S., with Iona Township’s place in South Dakota beside it.
What a year in Iona Township feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 156 frost-free days a year
In half of years the last 32° night comes by May 3 and the first by October 7. Frost and day counts come from NOAA’s station at Chamberlain 5 S, SD, 11 miles from the town’s center, at about the same height.
The 2023 USDA map puts Iona Township’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 43 inches of snow a winter
Snow, measured at Chamberlain 5 S, SD, falls mostly in January, February, March and December. Precipitation (rain plus melted snow) adds up to 23 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 93 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Iona Township
90% 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 Chamberlain 5 S, SD.
Living with Iona Township’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
156 frost-free days in zone 5a. The last frost comes by May 3 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 7.
Months with highs of 62–84° and lows of 40° or more: May, June and September. 89 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Iona Township from natural hazards, river flooding is the largest share (48%); heat waves, cold waves, winter storms and ice storms together are 35%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Iona Township and its neighbors
Oacoma Township has the coldest January nights next door (10°, 1° colder). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Iona Township’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 |
|---|---|---|---|---|
| Iona Township, SD | 11° | 88° | 23" | 43" |
| Alliance, NE | 13° | 88° | 17" | 45" |
| Providence, UT | 15° | 89° | 19" | 44" |
| Glenwood Springs, CO | 14° | 87° | 15" | 39" |
| Sheridan, WY | 11° | 89° | 15" | 33" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Iona Township averaged 1.3° warmer than the 1900s. The biggest change is in January (+3.7°).
A smaller shift than in 52% 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 Iona Township compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Iona Township’s place among South Dakota’s.
Iona Township weather by month
Highs, lows and precipitation from NOAA’s grid at Iona Township’s center; snow, wet days and snow on the ground from Chamberlain 5 S, SD. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 32° | 11° | 0.4" | 7.3" | 6 | 18 | 13° – 37° |
| February | 36° | 15° | 0.6" | 8.0" | 6 | 12 | 11° – 36° |
| March | 48° | 25° | 1.0" | 7.2" | 6 | 10 | 25° – 51° |
| April | 60° | 35° | 2.6" | 6.8" | 10 | 2 | 38° – 53° |
| May | 71° | 46° | 3.5" | 0.0" | 11 | 0 | 54° – 65° |
| June | 81° | 57° | 3.8" | 0.0" | 11 | 0 | 64° – 74° |
| July | 88° | 63° | 2.8" | 0.0" | 9 | 0 | 66° – 82° |
| August | 86° | 61° | 2.8" | 0.0" | 8 | 0 | 67° – 77° |
| September | 78° | 51° | 2.3" | 0.0" | 7 | 0 | 58° – 70° |
| October | 63° | 38° | 1.8" | 1.4" | 7 | 1 | 42° – 56° |
| November | 47° | 25° | 0.7" | 5.1" | 5 | 5 | 25° – 45° |
| December | 34° | 15° | 0.5" | 7.5" | 6 | 15 | 13° – 31° |
| Year | 60° | 37° | 22.7" | 43.3" | 93 | 64 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 25° to 51°. June is the most reliable, staying within 10°.
Where Iona Township’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 Iona Township’s center.
- Snow: Chamberlain 5 S, SD.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Chamberlain 5 S, SD, 11 miles from the town’s center, at about the same height; 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 Iona Township’s climate
What is the weather like in Iona Township?
A typical July afternoon reaches 88°, a January night drops to 11°, and about 43 inches of snow falls in a normal winter. Colder January nights than 92% of U.S. towns; hotter July afternoons than 68% of U.S. towns.
How cold does it get in Iona Township in winter?
January nights average 11°. About 166 nights a year reach 32° or below and 22 reach 0° or below. In the coldest January of the last 30 years the month averaged 13°.
How much snow does Iona Township get?
About 43 inches in a normal winter at Chamberlain 5 S, SD, most of it in January, February, March and December, with snow on the ground about 64 days a year.
How hot does it get in Iona Township?
July, with a typical high of 88° and a low of 63°. About 34 days a year reach 90° and 5 reach 100° (Chamberlain 5 S, SD).
When is the first and last frost in Iona Township?
In half of years the last spring frost (32°) comes by May 3 and the first fall frost by October 7, about 156 frost-free days, at Chamberlain 5 S, SD.
What growing zone is Iona Township 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 Iona Township?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Iona Township getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 52% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Iona Township.
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.