Photo: Wikigaurabia · CC BY-SA 3.0For weather, Grafton is about as ordinary as U.S. towns get
The warmest part of a July day comes in at 87° on average. In July, afternoons here are warmer than in 64% of U.S. towns. Decade by decade the climate has edged up, 0.9° above 1901–2000. If you like long walks, April, May, September and October offer highs of 66–79°.
A year in Grafton at a glance
Each month’s typical high and low, and what it brings.
What stands out about Grafton’s climate
Compared with towns across the U.S., with Grafton’s place in Illinois beside it.
What a year in Grafton feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 203 frost-free days a year
In half of years the last 32° night comes by April 5 and the first by October 27. Frost and day counts come from NOAA’s station at St Charles Co Airport, 3 miles from the town’s center, 210 ft lower.
The 2023 USDA map puts Grafton’s center in zone 6b: 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 9 inches of snow a winter
Snow, measured at St Charles Elm Pt, MO, falls mostly in January. Precipitation (rain plus melted snow) adds up to 42 inches a year; May is the wettest month and February the driest. Rain or snow falls on about 101 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Grafton
76% 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 St Charles Co Airport.
Living with Grafton’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
203 frost-free days in zone 6b. 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 27.
Months with highs of 62–84° and lows of 40° or more: April, May, September and October. 8.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Grafton from natural hazards, river flooding is the largest share (61%); heat waves, cold waves, winter storms and ice storms together are 23%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Grafton and similar climates
TownRatings has no climate map of the towns around Grafton yet.
Climates most like Grafton’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 |
|---|---|---|---|---|
| Grafton, IL | 22° | 87° | 42" | 9.0" |
| Belton, MO | 21° | 88° | 42" | 8.6" |
| Hamilton, OH | 22° | 87° | 43" | 9.7" |
| Mission, KS | 21° | 88° | 40" | 11" |
| Flatwoods, KY | 24° | 87° | 44" | 6.6" |
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 Grafton averaged 0.9° warmer than the 1900s. The biggest change is in December (+2.0°).
A smaller shift than in 86% 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 Grafton compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Grafton’s place among Illinois’.
Grafton weather by month
Highs, lows and precipitation from NOAA’s grid at Grafton’s center; snow, wet days and snow on the ground from St Charles Elm Pt, MO. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 38° | 22° | 2.3" | 4.3" | 8 | 24° – 41° |
| February | 44° | 26° | 2.2" | 2.6" | 7 | 24° – 44° |
| March | 54° | 34° | 3.2" | 0.5" | 10 | 37° – 58° |
| April | 66° | 44° | 4.6" | 0.0" | 10 | 48° – 61° |
| May | 76° | 55° | 4.9" | 0.0" | 11 | 60° – 73° |
| June | 84° | 64° | 4.4" | 0.0" | 9 | 69° – 78° |
| July | 87° | 68° | 3.9" | 0.0" | 8 | 72° – 84° |
| August | 86° | 66° | 3.7" | 0.0" | 7 | 70° – 82° |
| September | 79° | 58° | 3.4" | 0.0" | 7 | 64° – 75° |
| October | 68° | 46° | 3.2" | 0.0" | 8 | 52° – 63° |
| November | 54° | 36° | 3.3" | 0.1" | 8 | 37° – 52° |
| December | 43° | 26° | 2.5" | 1.5" | 7 | 21° – 43° |
| Year | 65° | 45° | 41.6" | 9.0" | 101 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 21° to 43°. June is the most reliable, staying within 9°.
Where Grafton’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 Grafton’s center.
- Snow: St Charles Elm Pt, MO.
- Frost, freezing nights, 90° and 100° days, heating and cooling: St Charles Co Airport, 3 miles from the town’s center, 210 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 Grafton’s climate
What is the weather like in Grafton?
A typical July afternoon reaches 87°, a January night drops to 22°, and about 9 inches of snow falls in a normal winter. Milder January nights than 50% of U.S. towns; hotter July afternoons than 64% of U.S. towns.
How cold does it get in Grafton in winter?
January nights average 22°. About 102 nights a year reach 32° or below and 2 reach 0° or below. In the coldest January of the last 30 years the month averaged 24°.
How much snow does Grafton get?
About 9.0 inches in a normal winter at St Charles Elm Pt, MO, most of it in January.
How hot does it get in Grafton?
July, with a typical high of 87° and a low of 68°. About 44 days a year reach 90° and 3 reach 100° (St Charles Co Airport).
When is the first and last frost in Grafton?
In half of years the last spring frost (32°) comes by April 5 and the first fall frost by October 27, about 203 frost-free days, at St Charles Co Airport.
What growing zone is Grafton in?
Zone 6b 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 Grafton?
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 Grafton getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 86% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Grafton.
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.