Photo: Kaethesson · CC BY-SA 3.0July in Oswego runs hotter than in 80% of U.S. towns
On a normal January night the air cools to about 25°. Seasons differ by 66°, from the coldest nights to the warmest afternoons. Its January nights stay gentler than in 62% of U.S. towns. Plan time outside for April, May, September and October, when highs sit at 69–82°.
A year in Oswego at a glance
Each month’s typical high and low, and what it brings.
What stands out about Oswego’s climate
Compared with towns across the U.S., with Oswego’s place in Kansas beside it.
What a year in Oswego feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 208 frost-free days a year
In half of years the last 32° night comes by April 5 and the first by October 31. Frost and day counts come from NOAA’s station at Columbus, KS, 15 miles from the town’s center, at about the same height.
The 2023 USDA map puts Oswego’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 1°. 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 4 inches of snow a winter
Snow, measured at Oswego 1 N, KS, falls mostly in January. Precipitation (rain plus melted snow) adds up to 45 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 85 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Oswego
74% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Columbus, KS.
Living with Oswego’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
208 frost-free days in zone 7a. The last frost comes by Apr 5 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 31.
Months with highs of 62–84° and lows of 40° or more: April, May, September and October.
Parks & trails →Of the yearly building losses FEMA expects in Oswego from natural hazards, river flooding is the largest share (43%); heat waves, cold waves, winter storms and ice storms together are 21%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Oswego and similar climates
TownRatings has no climate map of the towns around Oswego yet.
Climates most like Oswego’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 |
|---|---|---|---|---|
| Oswego, KS | 25° | 91° | 45" | 4.1" |
| Mountain Home, AR | 26° | 90° | 48" | 7.8" |
| Ste. Genevieve, MO | 24° | 89° | 43" | 4.3" |
| Butner, NC | 28° | 90° | 46" | 1.7" |
| Washington, DC | 27° | 89° | 44" | 5.8" |
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 Oswego averaged 0.6° warmer than the 1900s. The biggest change is in January (+2.0°).
A smaller shift than in 97% 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 Oswego compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Oswego’s place among Kansas’.
Oswego weather by month
Highs, lows and precipitation from NOAA’s grid at Oswego’s center; snow, wet days and snow on the ground from Oswego 1 N, KS. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 45° | 25° | 1.6" | 1.9" | 6 | 2 | 29° – 44° |
| February | 50° | 28° | 1.8" | 0.4" | 5 | 1 | 32° – 47° |
| March | 60° | 38° | 3.2" | 0.7" | 8 | 1 | 43° – 59° |
| April | 69° | 46° | 4.7" | 0.0" | 9 | 0 | 51° – 64° |
| May | 77° | 56° | 6.7" | 0.0" | 11 | 0 | 62° – 74° |
| June | 86° | 66° | 5.4" | 0.0" | 9 | 0 | 71° – 80° |
| July | 91° | 70° | 4.1" | 0.0" | 7 | 0 | 75° – 87° |
| August | 90° | 68° | 4.1" | 0.0" | 7 | 0 | 73° – 84° |
| September | 82° | 59° | 4.5" | 0.0" | 7 | 0 | 66° – 78° |
| October | 71° | 47° | 3.9" | 0.0" | 7 | 0 | 52° – 65° |
| November | 59° | 37° | 2.8" | 0.0" | 6 | 0 | 41° – 55° |
| December | 48° | 28° | 2.2" | 1.1" | 5 | 2 | 25° – 44° |
| Year | 69° | 47° | 44.9" | 4.1" | 85 | 7 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 25° to 44°. June is the most reliable, staying within 9°.
Where Oswego’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 Oswego’s center.
- Snow: Oswego 1 N, KS (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Columbus, KS, 15 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 Oswego’s climate
What is the weather like in Oswego?
A typical July afternoon reaches 91°, a January night drops to 25°, and about 4 inches of snow falls in a normal winter. Milder January nights than 62% of U.S. towns; hotter July afternoons than 80% of U.S. towns.
How cold does it get in Oswego in winter?
January nights average 25°. About 95 nights a year reach 32° or below and 1 reach 0° or below. In the coldest January of the last 30 years the month averaged 29°.
How much snow does Oswego get?
About 4.1 inches in a normal winter at Oswego 1 N, KS, most of it in January, with snow on the ground about 7 days a year.
How hot does it get in Oswego?
July, with a typical high of 91° and a low of 70°. About 46 days a year reach 90° and 4 reach 100° (Columbus, KS).
When is the first and last frost in Oswego?
In half of years the last spring frost (32°) comes by April 5 and the first fall frost by October 31, about 208 frost-free days, at Columbus, KS.
What growing zone is Oswego in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 1°.
What is the best time of year to visit Oswego?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Oswego getting warmer?
Yes: 1991–2020 averaged 0.6° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 97% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Oswego.
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.