Photo: Jeffrey Beall · CC BY-SA 3.0San Luis sits near the bottom of U.S. towns for winter warmth
Midsummer highs settle at about 81°. A year here swings 72° from midwinter lows to midsummer highs. It is a dry place: less rain and snow fall here than on 93% of U.S. towns. Long walks are most pleasant from June to August, when afternoons reach 78–81°.
A year in San Luis at a glance
Each month’s typical high and low, and what it brings.
What stands out about San Luis’ climate
Compared with towns across the U.S., with San Luis’ place in Colorado beside it.
What a year in San Luis feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 115 frost-free days a year
In half of years the last 32° night comes by May 31 and the first by September 23. Frost and day counts come from NOAA’s station at San Luis 1 S, CO, 0.5 miles from the town’s center, at about the same height.
The 2023 USDA map puts San Luis’ center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −13°. 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 16 inches of rain a year
August is the wettest month and February the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in San Luis
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 San Luis 1 S, CO.
Living with San Luis’ climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
115 frost-free days in zone 5b. The last frost comes by May 31 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 23.
Months with highs of 62–84° and lows of 40° or more: June, July and August.
Parks & trails →Of the yearly building losses FEMA expects in San Luis from natural hazards, river flooding is the largest share (59%); heat waves, cold waves, winter storms and ice storms together are 9%. Normals are averages; the hazards page covers the extremes.
Natural hazards →San Luis and similar climates
TownRatings has no climate map of the towns around San Luis yet.
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 San Luis averaged 1.6° warmer than the 1900s. The biggest change is in March (+3.1°).
A bigger shift than in 66% 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 San Luis compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with San Luis’ place among Colorado’s.
San Luis weather by month
Highs, lows and precipitation from NOAA’s grid at San Luis’ center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 38° | 9° | 0.9" | 17° – 29° |
| February | 42° | 13° | 0.8" | 22° – 33° |
| March | 50° | 21° | 1.0" | 31° – 41° |
| April | 58° | 26° | 1.2" | 37° – 47° |
| May | 67° | 34° | 1.4" | 46° – 56° |
| June | 78° | 42° | 1.0" | 56° – 64° |
| July | 81° | 48° | 2.2" | 61° – 69° |
| August | 78° | 46° | 2.3" | 59° – 66° |
| September | 72° | 39° | 1.7" | 50° – 59° |
| October | 62° | 29° | 1.3" | 41° – 50° |
| November | 49° | 19° | 0.9" | 26° – 41° |
| December | 39° | 10° | 1.0" | 20° – 30° |
| Year | 59° | 28° | 15.6" |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 26° to 41°. August is the most reliable, staying within 7°.
Where San Luis’ 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 San Luis’ center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: San Luis 1 S, CO, 0.5 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 San Luis’ climate
What is the weather like in San Luis?
A typical July afternoon reaches 81°, a January night drops to 9°. Colder January nights than 95% of U.S. towns; cooler July afternoons than 88% of U.S. towns.
How cold does it get in San Luis in winter?
January nights average 9°. About 211 nights a year reach 32° or below and 23 reach 0° or below. In the coldest January of the last 30 years the month averaged 17°.
How hot does it get in San Luis?
July, with a typical high of 81° and a low of 48°. About 2 days a year reach 90° (San Luis 1 S, CO).
When is the first and last frost in San Luis?
In half of years the last spring frost (32°) comes by May 31 and the first fall frost by September 23, about 115 frost-free days, at San Luis 1 S, CO.
What growing zone is San Luis in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −13°.
What is the best time of year to visit San Luis?
By one simple rule (highs of 62–84° and lows of 40° or more), June, July and August. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is San Luis getting warmer?
Yes: 1991–2020 averaged 1.6° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 66% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in San Luis.
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.