Jacob Wingard Dreher House · Photo: Bill Fitzpatrick · CC BY-SA 3.0Summer arrives in force in Irmo, hotter than in 90% of U.S. towns
On a normal January night the air cools to about 34°. Its January nights stay gentler than in 79% of U.S. towns. Warming shows here too: 1.1° more than in 1901–2000, led by February. From March to May and October to November, highs of 66–84° make it easy to spend the day outdoors.
A year in Irmo at a glance
Each month’s typical high and low, and what it brings.
What stands out about Irmo’s climate
Compared with towns across the U.S., with Irmo’s place in South Carolina beside it.
What a year in Irmo feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 229 frost-free days a year
In half of years the last 32° night comes by March 25 and the first by November 7. Frost and day counts come from NOAA’s station at Columbia, SC, 11 miles from the town’s center, 120 ft lower.
The 2023 USDA map puts Irmo’s center in zone 8b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 16°. 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 1 inches of snow a winter
Snow, measured at Columbia, SC, falls mostly in January. Precipitation (rain plus melted snow) adds up to 45 inches a year; June is the wettest month and April the driest. Rain or snow falls on about 109 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Irmo
53% of the work is heating. Months averaging under 55° run from November through February.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Columbia, SC.
Living with Irmo’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
229 frost-free days in zone 8b. The last frost comes by Mar 25 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 7.
Months with highs of 62–84° and lows of 40° or more: March, April, May, October and November. 0.8 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Irmo from natural hazards, river flooding is the largest share (52%); heat waves, cold waves, winter storms and ice storms together are 11%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Irmo and its neighbors
Every town next door is within a degree of Irmo in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Irmo’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 |
|---|---|---|---|---|
| Irmo, SC | 34° | 93° | 45" | 1.2" |
| Sulphur Springs, TX | 34° | 94° | 45" | 1.6" |
| Durant, OK | 32° | 94° | 43" | 2.0" |
| Macon-Bibb County, GA | 35° | 92° | 47" | 0.0" |
| Clearlake, CA | 35° | 93° | 40" | 0.4" |
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 Irmo averaged 1.1° warmer than the 1900s. The biggest change is in February (+2.0°).
A smaller shift than in 70% 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 Irmo compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Irmo’s place among South Carolina’s.
Irmo weather by month
Highs, lows and precipitation from NOAA’s grid at Irmo’s center; snow, wet days and snow on the ground from Columbia, SC. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 56° | 34° | 3.8" | 0.6" | 10 | 1 | 40° – 51° |
| February | 60° | 37° | 3.6" | 0.4" | 9 | 0 | 41° – 58° |
| March | 68° | 43° | 3.9" | 0.1" | 9 | 0 | 49° – 64° |
| April | 77° | 50° | 3.0" | 0.0" | 8 | 0 | 59° – 68° |
| May | 84° | 59° | 3.3" | 0.0" | 9 | 0 | 67° – 76° |
| June | 90° | 67° | 4.6" | 0.0" | 11 | 0 | 74° – 82° |
| July | 93° | 71° | 4.4" | 0.0" | 12 | 0 | 79° – 85° |
| August | 91° | 70° | 4.5" | 0.0" | 10 | 0 | 77° – 85° |
| September | 85° | 64° | 4.0" | 0.0" | 8 | 0 | 71° – 80° |
| October | 76° | 52° | 3.3" | 0.0" | 7 | 0 | 60° – 69° |
| November | 66° | 41° | 3.1" | 0.0" | 7 | 0 | 49° – 59° |
| December | 58° | 36° | 3.9" | 0.1" | 9 | 0 | 38° – 58° |
| Year | 75° | 52° | 45.4" | 1.2" | 109 | 1 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 38° to 58°. July is the most reliable, staying within 7°.
Where Irmo’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 Irmo’s center.
- Snow: Columbia, SC.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Columbia, SC, 11 miles from the town’s center, 120 ft lower; 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 Irmo’s climate
What is the weather like in Irmo?
A typical July afternoon reaches 93°, a January night drops to 34°, and about 1 inches of snow falls in a normal winter. Milder January nights than 79% of U.S. towns; hotter July afternoons than 90% of U.S. towns.
How cold does it get in Irmo in winter?
January nights average 34°. About 47 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 40°.
How much snow does Irmo get?
About 1.2 inches in a normal winter at Columbia, SC, most of it in January, with snow on the ground about 1 days a year.
How hot does it get in Irmo?
July, with a typical high of 93° and a low of 71°. About 81 days a year reach 90° and 6 reach 100° (Columbia, SC).
When is the first and last frost in Irmo?
In half of years the last spring frost (32°) comes by March 25 and the first fall frost by November 7, about 229 frost-free days, at Columbia, SC.
What growing zone is Irmo in?
Zone 8b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 16°.
What is the best time of year to visit Irmo?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Irmo getting warmer?
Yes: 1991–2020 averaged 1.1° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 70% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Irmo.
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.