Photo: Mitchazenia · CC BY-SA 4.0January in New Boston bites harder than in 85% of U.S. towns
Peak summer warmth arrives in July, with afternoons near 85°. It is a dry place: less rain and snow fall here than on 71% of U.S. towns. Warming shows here too: 0.6° more than in 1901–2000, led by December. Keep the boiler serviced for the months from November to March, which average under 50°.
A year in New Boston at a glance
Each month’s typical high and low, and what it brings.
What stands out about New Boston’s climate
Compared with towns across the U.S., with New Boston’s place in Illinois beside it.
What a year in New Boston feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 190 frost-free days a year
In half of years the last 32° night comes by April 14 and the first by October 24. Frost and day counts come from NOAA’s station at New Boston Dam 17, IL, 3 miles from the town’s center, at about the same height.
The 2023 USDA map puts New Boston’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −10°. 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 20 inches of snow a winter
Snow, measured at Keithsburg, IL, falls mostly in January. Precipitation (rain plus melted snow) adds up to 37 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 82 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in New Boston
85% 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 New Boston Dam 17, IL.
Living with New Boston’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
190 frost-free days in zone 5b. The last frost comes by Apr 14 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 24.
Months with highs of 62–84° and lows of 40° or more: May, June, August, September and October.
Parks & trails →Of the yearly building losses FEMA expects in New Boston from natural hazards, river flooding is the largest share (38%); heat waves, cold waves, winter storms and ice storms together are 19%. Normals are averages; the hazards page covers the extremes.
Natural hazards →New Boston and its neighbors
Every town next door is within a degree of New Boston in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like New Boston’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 |
|---|---|---|---|---|
| New Boston, IL | 15° | 85° | 37" | 20" |
| Clarinda, IA | 14° | 86° | 36" | 23" |
| Defiance, OH | 19° | 85° | 37" | 24" |
| Savannah, MO | 18° | 87° | 37" | 21" |
| West Lafayette, IN | 18° | 84° | 40" | 19" |
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 New Boston averaged 0.6° warmer than the 1900s. The biggest change is in December (+1.8°).
A smaller shift than in 96% 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 New Boston compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with New Boston’s place among Illinois’.
New Boston weather by month
Highs, lows and precipitation from NOAA’s grid at New Boston’s center; snow, wet days and snow on the ground from Keithsburg, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 31° | 15° | 1.4" | 6.8" | 6 | 15° – 36° |
| February | 36° | 19° | 1.7" | 3.9" | 6 | 14° – 39° |
| March | 49° | 29° | 2.5" | 3.4" | 7 | 31° – 53° |
| April | 63° | 40° | 3.6" | 0.6" | 9 | 42° – 59° |
| May | 73° | 51° | 4.9" | 0.0" | 10 | 56° – 69° |
| June | 82° | 61° | 5.0" | 0.0" | 8 | 69° – 75° |
| July | 85° | 65° | 3.9" | 0.0" | 7 | 70° – 81° |
| August | 83° | 63° | 3.9" | 0.0" | 7 | 67° – 78° |
| September | 77° | 54° | 3.5" | 0.0" | 6 | 60° – 71° |
| October | 64° | 43° | 2.9" | 0.0" | 5 | 48° – 59° |
| November | 49° | 31° | 2.3" | 0.5" | 6 | 32° – 50° |
| December | 36° | 21° | 1.8" | 5.2" | 6 | 13° – 38° |
| Year | 61° | 41° | 37.3" | 20.4" | 82 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 13° to 38°. June is the most reliable, staying within 6°.
Where New Boston’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 New Boston’s center.
- Snow: Keithsburg, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: New Boston Dam 17, IL, 3 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 New Boston’s climate
What is the weather like in New Boston?
A typical July afternoon reaches 85°, a January night drops to 15°, and about 20 inches of snow falls in a normal winter. Colder January nights than 85% of U.S. towns; cooler July afternoons than 50% of U.S. towns.
How cold does it get in New Boston in winter?
January nights average 15°. About 122 nights a year reach 32° or below and 9 reach 0° or below. In the coldest January of the last 30 years the month averaged 15°.
How much snow does New Boston get?
About 20 inches in a normal winter at Keithsburg, IL, most of it in January.
How hot does it get in New Boston?
July, with a typical high of 85° and a low of 65°. About 24 days a year reach 90° (New Boston Dam 17, IL).
When is the first and last frost in New Boston?
In half of years the last spring frost (32°) comes by April 14 and the first fall frost by October 24, about 190 frost-free days, at New Boston Dam 17, IL.
What growing zone is New Boston in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −10°.
What is the best time of year to visit New Boston?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is New Boston getting warmer?
Yes: 1991–2020 averaged 0.6° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 96% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in New Boston.
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.