Hardly any U.S. towns see harsher January nights than Onaka
Peak summer warmth arrives in July, with afternoons near 84°. From frosty January to warm July, readings climb 80°. It is a dry place: less rain and snow fall here than on 89% of U.S. towns. Radiators earn their keep from October to April, the months that average under 50°.
A year in Onaka at a glance
Each month’s typical high and low, and what it brings.
What stands out about Onaka’s climate
Compared with towns across the U.S., with Onaka’s place in South Dakota beside it.
What a year in Onaka feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 148 frost-free days a year
In half of years the last 32° night comes by May 7 and the first by October 3. Frost and day counts come from NOAA’s station at Roscoe, SD, 19 miles from the town’s center, at about the same height.
The 2023 USDA map puts Onaka’s center in zone 4b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −23°. 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 Onaka, SD, falls mostly in January. Precipitation (rain plus melted snow) adds up to 20 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 55 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Onaka
94% 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 Roscoe, SD.
Living with Onaka’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
148 frost-free days in zone 4b. The last frost comes by May 7 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 3.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September.
Parks & trails →Cold waves are 42% of the yearly building losses FEMA expects in Onaka from natural hazards, the largest share. Normals are averages; the hazards page covers the extremes.
Natural hazards →Onaka and similar climates
TownRatings has no climate map of the towns around Onaka yet.
Climates most like Onaka’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 |
|---|---|---|---|---|
| Onaka, SD | 4° | 84° | 20" | 35" |
| Dickinson, ND | 5° | 83° | 16" | 35" |
| Sidney, MT | 4° | 85° | 15" | 30" |
| Montevideo, MN | 4° | 83° | 28" | 46" |
| Sioux Center, IA | 8° | 84° | 29" | 35" |
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 Onaka averaged 0.8° warmer than the 1900s. The biggest change is in January (+3.3°).
A smaller shift than in 87% 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 Onaka compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Onaka’s place among South Dakota’s.
Onaka weather by month
Highs, lows and precipitation from NOAA’s grid at Onaka’s center; snow, wet days and snow on the ground from Onaka, SD. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 23° | 4° | 0.4" | 7.4" | 3 | 2° – 29° |
| February | 28° | 8° | 0.6" | 6.3" | 3 | 1° – 30° |
| March | 41° | 19° | 0.9" | 5.1" | 4 | 20° – 44° |
| April | 55° | 30° | 1.8" | 5.7" | 5 | 34° – 49° |
| May | 68° | 42° | 3.1" | 0.1" | 7 | 50° – 62° |
| June | 77° | 53° | 3.5" | 0.0" | 8 | 60° – 70° |
| July | 84° | 58° | 2.9" | 0.0" | 6 | 62° – 78° |
| August | 82° | 56° | 2.3" | 0.0" | 5 | 64° – 73° |
| September | 73° | 47° | 1.9" | 0.0" | 5 | 54° – 65° |
| October | 57° | 34° | 1.8" | 0.4" | 5 | 38° – 51° |
| November | 41° | 20° | 0.6" | 4.8" | 3 | 18° – 40° |
| December | 28° | 10° | 0.5" | 5.2" | 3 | 5° – 27° |
| Year | 55° | 32° | 20.4" | 35.0" | 55 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 1° to 30°. June is the most reliable, staying within 9°.
Where Onaka’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 Onaka’s center.
- Snow: Onaka, SD (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Roscoe, SD, 19 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 Onaka’s climate
What is the weather like in Onaka?
A typical July afternoon reaches 84°, a January night drops to 4°, and about 35 inches of snow falls in a normal winter. Colder January nights than all but 165 U.S. towns; cooler July afternoons than 63% of U.S. towns.
How cold does it get in Onaka in winter?
January nights average 4°. About 182 nights a year reach 32° or below and 37 reach 0° or below. In the coldest January of the last 30 years the month averaged 2°.
How much snow does Onaka get?
About 35 inches in a normal winter at Onaka, SD, most of it in January.
How hot does it get in Onaka?
July, with a typical high of 84° and a low of 58°. About 14 days a year reach 90° and 1 reach 100° (Roscoe, SD).
When is the first and last frost in Onaka?
In half of years the last spring frost (32°) comes by May 7 and the first fall frost by October 3, about 148 frost-free days, at Roscoe, SD.
What growing zone is Onaka in?
Zone 4b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −23°.
What is the best time of year to visit Onaka?
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 Onaka getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 87% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Onaka.
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.