Altona gets about 85 inches of snow a winter, more than 96% of U.S. towns
Expect July afternoons of about 84°. The gap between a January night and a July afternoon is 64°. It is a dry place: less rain and snow fall here than on 91% of U.S. towns. Comfortable outdoor weather, highs of 67–82°, belongs to May, June, August and September.
A year in Altona at a glance
Each month’s typical high and low, and what it brings.
What stands out about Altona’s climate
Compared with towns across the U.S., with Altona’s place in Colorado beside it.
What a year in Altona feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 151 frost-free days a year
In half of years the last 32° night comes by May 6 and the first by October 5. Frost and day counts come from NOAA’s station at Boulder, CO, 9 miles from the town’s center, 270 ft lower.
The 2023 USDA map puts Altona’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −8°. 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 85 inches of snow a winter
Snow, measured at Boulder 2.9 S, CO, falls mostly in February. Precipitation (rain plus melted snow) adds up to 18 inches a year; May is the wettest month and December the driest. Rain or snow falls on about 94 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Altona
90% 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 Boulder, CO.
Living with Altona’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
151 frost-free days in zone 6a. The last frost comes by May 6 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 5.
Months with highs of 62–84° and lows of 40° or more: May, June, August and September.
Parks & trails →Of the yearly building losses FEMA expects in Altona from natural hazards, wildfire is the largest share (46%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Altona and similar climates
TownRatings has no climate map of the towns around Altona yet.
Climates most like Altona’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 |
|---|---|---|---|---|
| Altona, CO | 20° | 84° | 18" | 85" |
| Flagstaff, AZ | 16° | 84° | 18" | 90" |
| Four Corners, MT | 14° | 84° | 15" | 91" |
| Pocatello, ID | 19° | 87° | 15" | 64" |
| Spearfish, SD | 15° | 86° | 25" | 71" |
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 Altona averaged 1.4° warmer than the 1900s. The biggest change is in March (+3.1°).
A bigger shift than in 51% 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 Altona compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Altona’s place among Colorado’s.
Altona weather by month
Highs, lows and precipitation from NOAA’s grid at Altona’s center; snow, wet days and snow on the ground from Boulder 2.9 S, CO. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 44° | 20° | 0.6" | 10.2" | 6 | 25° – 38° |
| February | 44° | 21° | 0.7" | 17.4" | 8 | 28° – 40° |
| March | 52° | 28° | 1.5" | 13.6" | 7 | 34° – 46° |
| April | 58° | 33° | 2.3" | 11.9" | 8 | 40° – 50° |
| May | 67° | 42° | 2.8" | 2.5" | 12 | 49° – 58° |
| June | 78° | 50° | 1.9" | 0.0" | 9 | 60° – 70° |
| July | 84° | 56° | 2.1" | 0.0" | 10 | 66° – 74° |
| August | 82° | 54° | 1.9" | 0.0" | 10 | 64° – 72° |
| September | 75° | 47° | 1.6" | 0.0" | 7 | 56° – 65° |
| October | 62° | 36° | 1.2" | 6.9" | 7 | 42° – 55° |
| November | 51° | 28° | 0.9" | 8.5" | 5 | 30° – 46° |
| December | 43° | 21° | 0.6" | 14.2" | 6 | 25° – 35° |
| Year | 62° | 36° | 17.9" | 85.2" | 94 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 30° to 46°. August is the most reliable, staying within 8°.
Where Altona’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 Altona’s center.
- Snow: Boulder 2.9 S, CO.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Boulder, CO, 9 miles from the town’s center, 270 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 Altona’s climate
What is the weather like in Altona?
A typical July afternoon reaches 84°, a January night drops to 20°, and about 85 inches of snow falls in a normal winter. Colder January nights than 57% of U.S. towns; cooler July afternoons than 58% of U.S. towns.
How cold does it get in Altona in winter?
January nights average 20°. About 138 nights a year reach 32° or below and 4 reach 0° or below. In the coldest January of the last 30 years the month averaged 25°.
How much snow does Altona get?
About 85 inches in a normal winter at Boulder 2.9 S, CO, most of it in February.
How hot does it get in Altona?
July, with a typical high of 84° and a low of 56°. About 33 days a year reach 90° (Boulder, CO).
When is the first and last frost in Altona?
In half of years the last spring frost (32°) comes by May 6 and the first fall frost by October 5, about 151 frost-free days, at Boulder, CO.
What growing zone is Altona in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −8°.
What is the best time of year to visit Altona?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Altona getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 51% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Altona.
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.