Photo: Cathy from USA · CC BY-SA 2.0San Ysidro is among the driest of U.S. towns: 10 inches of precipitation a year
January mornings start at about 19°. Its July heat outdoes that of 89% of U.S. towns. The latest 30-year average runs 1.3° warmer than 1901–2000’s, with March up the most. Radiators earn their keep from November to March, the months that average under 50°.
A year in San Ysidro at a glance
Each month’s typical high and low, and what it brings.
What stands out about San Ysidro’s climate
Compared with towns across the U.S., with San Ysidro’s place in New Mexico beside it.
What a year in San Ysidro feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 188 frost-free days a year
In half of years the last 32° night comes by April 17 and the first by October 24. Frost and day counts come from NOAA’s station at Jemez Dam, NM, 18 miles from the town’s center, at about the same height.
The 2023 USDA map puts San Ysidro’s center in zone 7b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 5°. 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 6 inches of snow a winter
Snow, measured at Jemez Dam, NM, falls mostly in December. Precipitation (rain plus melted snow) adds up to 10 inches a year; August is the wettest month and February the driest. Rain or snow falls on about 50 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in San Ysidro
78% of the work is heating. 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 Jemez Dam, NM.
Living with San Ysidro’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
188 frost-free days in zone 7b. The last frost comes by Apr 17 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 and September.
Parks & trails →Of the yearly building losses FEMA expects in San Ysidro from natural hazards, river flooding is the largest share (54%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →San Ysidro and similar climates
TownRatings has no climate map of the towns around San Ysidro yet.
Climates most like San Ysidro’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 |
|---|---|---|---|---|
| San Ysidro, NM | 19° | 92° | 10" | 5.7" |
| Star, ID | 24° | 93° | 11" | 7.4" |
| Spanish Springs, NV | 25° | 91° | 10" | 6.8" |
| Fruitvale, CO | 19° | 94° | 10" | 13" |
| Price, UT | 14° | 92° | 9" | 8.7" |
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 Ysidro averaged 1.3° warmer than the 1900s. The biggest change is in March (+2.5°).
A smaller 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 San Ysidro compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with San Ysidro’s place among New Mexico’s.
San Ysidro weather by month
Highs, lows and precipitation from NOAA’s grid at San Ysidro’s center; snow, wet days and snow on the ground from Jemez Dam, NM. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 48° | 19° | 0.4" | 0.8" | 4 | 0 | 28° – 39° |
| February | 54° | 24° | 0.3" | 0.7" | 3 | 0 | 33° – 44° |
| March | 63° | 30° | 0.5" | 0.9" | 3 | 0 | 43° – 51° |
| April | 70° | 35° | 0.5" | 0.0" | 3 | 0 | 49° – 57° |
| May | 80° | 44° | 0.6" | 0.0" | 3 | 0 | 58° – 67° |
| June | 91° | 53° | 0.5" | 0.0" | 3 | 0 | 67° – 76° |
| July | 92° | 59° | 1.7" | 0.0" | 8 | 0 | 73° – 80° |
| August | 90° | 58° | 1.7" | 0.0" | 7 | 0 | 71° – 78° |
| September | 83° | 50° | 1.3" | 0.0" | 6 | 0 | 61° – 70° |
| October | 72° | 38° | 1.1" | 0.0" | 4 | 0 | 52° – 59° |
| November | 58° | 27° | 0.6" | 0.3" | 2 | 0 | 35° – 49° |
| December | 47° | 19° | 0.5" | 3.0" | 4 | 1 | 29° – 39° |
| Year | 71° | 38° | 9.6" | 5.7" | 50 | 2 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 35° to 49°. August is the most reliable, staying within 7°.
Where San Ysidro’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 San Ysidro’s center.
- Snow: Jemez Dam, NM.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Jemez Dam, NM, 18 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 Ysidro’s climate
What is the weather like in San Ysidro?
A typical July afternoon reaches 92°, a January night drops to 19°, and about 6 inches of snow falls in a normal winter. Colder January nights than 63% of U.S. towns; hotter July afternoons than 89% of U.S. towns.
How cold does it get in San Ysidro in winter?
January nights average 19°. About 125 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 28°.
How much snow does San Ysidro get?
About 5.7 inches in a normal winter at Jemez Dam, NM, most of it in December, with snow on the ground about 2 days a year.
How hot does it get in San Ysidro?
July, with a typical high of 92° and a low of 59°. About 71 days a year reach 90° and 5 reach 100° (Jemez Dam, NM).
When is the first and last frost in San Ysidro?
In half of years the last spring frost (32°) comes by April 17 and the first fall frost by October 24, about 188 frost-free days, at Jemez Dam, NM.
What growing zone is San Ysidro in?
Zone 7b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 5°.
What is the best time of year to visit San Ysidro?
By one simple rule (highs of 62–84° and lows of 40° or more), May and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is San Ysidro getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 51% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in San Ysidro.
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.