John Hepburn Place · Photo: Magicpiano · CC BY-SA 4.0Precipitation in South Glastonbury trails that of 94% of U.S. towns: 14 inches a year
January nights here settle around 14°. Winter nights are cold: in January they are colder than in 88% of U.S. towns. Since 1901–2000, the year has warmed by 1.4°, most of all in January. Homes need heating from October to April, the months averaging under 50°.
A year in South Glastonbury at a glance
Each month’s typical high and low, and what it brings.
What stands out about South Glastonbury’s climate
Compared with towns across the U.S., with South Glastonbury’s place in Montana beside it.
What a year in South Glastonbury feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 102 frost-free days a year
In half of years the last 32° night comes by June 3 and the first by September 14. Day counts come from NOAA’s station at Gardiner, MT, 20 miles from the town’s center, at about the same height; frost dates and degree days from Yellowstone Park Mammoth, WY, 24 miles away.
The 2023 USDA map puts South Glastonbury’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −18°. 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 72 inches of snow a winter
Snow, measured at Yellowstone Park Mammoth, WY, falls mostly in January, February and December. Precipitation (rain plus melted snow) adds up to 14 inches a year; June is the wettest month and February the driest. Rain or snow falls on about 127 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in South Glastonbury
99% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through May.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Yellowstone Park Mammoth, WY.
Living with South Glastonbury’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
102 frost-free days in zone 5a. The last frost comes by Jun 3 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Sep 14.
Months with highs of 62–84° and lows of 40° or more: June and August.
Parks & trails →Of the yearly building losses FEMA expects in South Glastonbury from natural hazards, avalanches are the largest share (82%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →South Glastonbury and similar climates
TownRatings has no climate map of the towns around South Glastonbury yet.
Climates most like South Glastonbury’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 |
|---|---|---|---|---|
| South Glastonbury, MT | 14° | 84° | 14" | 72" |
| Ranchettes, WY | 16° | 85° | 16" | 65" |
| Durango, CO | 12° | 86° | 18" | 64" |
| Flagstaff, AZ | 16° | 84° | 18" | 90" |
| Hailey, ID | 10° | 84° | 14" | 102" |
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 South Glastonbury averaged 1.4° warmer than the 1900s. The biggest change is in January (+4.0°).
A bigger shift than in 55% 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 South Glastonbury compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with South Glastonbury’s place among Montana’s.
South Glastonbury weather by month
Highs, lows and precipitation from NOAA’s grid at South Glastonbury’s center; snow, wet days and snow on the ground from Yellowstone Park Mammoth, WY. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 34° | 14° | 0.6" | 11.5" | 11 | 31 | 18° – 29° |
| February | 38° | 15° | 0.5" | 11.5" | 11 | 27 | 19° – 33° |
| March | 47° | 23° | 0.9" | 10.9" | 11 | 19 | 29° – 41° |
| April | 55° | 29° | 1.6" | 7.8" | 11 | 6 | 36° – 47° |
| May | 65° | 37° | 2.1" | 1.7" | 13 | 1 | 46° – 55° |
| June | 74° | 44° | 2.2" | 0.3" | 13 | 0 | 52° – 65° |
| July | 84° | 49° | 1.2" | 0.0" | 9 | 0 | 57° – 73° |
| August | 83° | 47° | 1.0" | 0.0" | 9 | 0 | 60° – 69° |
| September | 73° | 39° | 1.1" | 0.6" | 9 | 0 | 52° – 60° |
| October | 58° | 30° | 1.3" | 4.7" | 10 | 3 | 35° – 51° |
| November | 43° | 21° | 0.7" | 9.9" | 10 | 16 | 24° – 41° |
| December | 33° | 13° | 0.6" | 12.6" | 12 | 28 | 17° – 27° |
| Year | 57° | 30° | 13.7" | 71.5" | 127 | 131 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 24° to 41°. September is the most reliable, staying within 8°.
Where South Glastonbury’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 South Glastonbury’s center.
- Snow: Yellowstone Park Mammoth, WY.
- Frost dates, heating and cooling: Yellowstone Park Mammoth, WY, 24 miles away.
- Freezing nights, 90° and 100° days: Gardiner, MT, 20 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 South Glastonbury’s climate
What is the weather like in South Glastonbury?
A typical July afternoon reaches 84°, a January night drops to 14°, and about 72 inches of snow falls in a normal winter. Colder January nights than 88% of U.S. towns; cooler July afternoons than 59% of U.S. towns.
How cold does it get in South Glastonbury in winter?
December nights average 13°. About 167 nights a year reach 32° or below and 10 reach 0° or below. In the coldest December of the last 30 years the month averaged 17°.
How much snow does South Glastonbury get?
About 72 inches in a normal winter at Yellowstone Park Mammoth, WY, most of it in January, February and December, with snow on the ground about 131 days a year.
How hot does it get in South Glastonbury?
July, with a typical high of 84° and a low of 49°. About 26 days a year reach 90° (Yellowstone Park Mammoth, WY).
When is the first and last frost in South Glastonbury?
In half of years the last spring frost (32°) comes by June 3 and the first fall frost by September 14, about 102 frost-free days, at Yellowstone Park Mammoth, WY.
What growing zone is South Glastonbury in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −18°.
What is the best time of year to visit South Glastonbury?
By one simple rule (highs of 62–84° and lows of 40° or more), June and August. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is South Glastonbury getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 55% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in South Glastonbury.
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.