Few U.S. towns get less rain and snow than Casa de Oro-Mount Helix: 13 inches a year
The coldest hours of a January night bottom out at 44° on average. By January nights alone, it runs milder than 92% of U.S. towns. Since 1901–2000, the year has warmed by 2.2°, most of all in January. Long walks are most pleasant from October to June, when afternoons reach 68–80°.
A year in Casa de Oro-Mount Helix at a glance
Each month’s typical high and low, and what it brings.
What stands out about Casa de Oro-Mount Helix’s climate
Compared with towns across the U.S., with Casa de Oro-Mount Helix’s place in California beside it.
What a year in Casa de Oro-Mount Helix feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
A freeze most winters
Frost and day counts come from NOAA’s station at El Cajon, CA, 3 miles from the town’s center, 190 ft lower.
The 2023 USDA map puts Casa de Oro-Mount Helix’s center in zone 10b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 37°. 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 13 inches of rain a year
February is the wettest month and July the driest. Rain falls on about 45 days a year. Snow is rare: about 0.0" in a normal year at Lakeside 2 E, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Casa de Oro-Mount Helix
49% of the work is heating, so air conditioning is the bigger bill. No month averages under 55°.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at El Cajon, CA.
Living with Casa de Oro-Mount Helix’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 10b. Frost comes about 7 winters in 10, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: January, February, March, April, May, June, October, November and December. 1.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Casa de Oro-Mount Helix from natural hazards, river flooding is the largest share (73%); heat waves, cold waves, winter storms and ice storms together are 5%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Casa de Oro-Mount Helix and its neighbors
Rancho San Diego the hottest July afternoons (86°, 2° warmer). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Casa de Oro-Mount Helix’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 |
|---|---|---|---|---|
| Casa de Oro-Mount Helix, CA | 44° | 85° | 13" | 0.0" |
| The Dalles, OR | 31° | 88° | 15" | 5.5" |
| Sierra Vista Southeast, AZ | 32° | 91° | 15" | 0.7" |
| Alpine, TX | 30° | 90° | 15" | 2.2" |
| Ewa Beach, HI | 62° | 87° | 17" | 0.0" |
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 Casa de Oro-Mount Helix averaged 2.2° warmer than the 1900s. The biggest change is in January (+3.2°).
A bigger shift than in 95% 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 Casa de Oro-Mount Helix compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Casa de Oro-Mount Helix’s place among California’s.
Casa de Oro-Mount Helix weather by month
Highs, lows and precipitation from NOAA’s grid at Casa de Oro-Mount Helix’s center; snow, wet days and snow on the ground from Lakeside 2 E, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 69° | 44° | 2.5" | 0.0" | 7 | 0 | 53° – 61° |
| February | 68° | 45° | 2.8" | 0.0" | 8 | 0 | 53° – 62° |
| March | 70° | 47° | 2.0" | 0.0" | 7 | 0 | 54° – 65° |
| April | 73° | 50° | 1.0" | 0.0" | 4 | 0 | 57° – 66° |
| May | 75° | 55° | 0.4" | 0.0" | 3 | 0 | 61° – 70° |
| June | 80° | 58° | 0.1" | 0.0" | 1 | 0 | 65° – 73° |
| July | 85° | 62° | 0.0" | 0.0" | 1 | 0 | 70° – 79° |
| August | 87° | 63° | 0.0" | 0.0" | 0 | 0 | 72° – 78° |
| September | 86° | 61° | 0.1" | 0.0" | 1 | 0 | 70° – 77° |
| October | 80° | 55° | 0.5" | 0.0" | 3 | 0 | 64° – 73° |
| November | 74° | 48° | 1.1" | 0.0" | 4 | 0 | 55° – 65° |
| December | 68° | 43° | 2.0" | 0.0" | 7 | 0 | 52° – 59° |
| Year | 76° | 52° | 12.6" | 0.0" | 45 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 54° to 65°. August is the most reliable, staying within 7°.
Where Casa de Oro-Mount Helix’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 Casa de Oro-Mount Helix’s center.
- Snow: Lakeside 2 E, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: El Cajon, CA, 3 miles from the town’s center, 190 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 Casa de Oro-Mount Helix’s climate
What is the weather like in Casa de Oro-Mount Helix?
A typical July afternoon reaches 85°, a January night drops to 44°, and snow is almost unheard of. Milder January nights than 92% of U.S. towns; cooler July afternoons than 55% of U.S. towns.
How cold does it get in Casa de Oro-Mount Helix in winter?
December nights average 43°. About 3 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 52°.
How much snow does Casa de Oro-Mount Helix get?
About 0.0 inches in a normal winter at Lakeside 2 E, CA, so most winters see none.
How hot does it get in Casa de Oro-Mount Helix?
July, with a typical high of 85° and a low of 62°. About 57 days a year reach 90° and 7 reach 100° (El Cajon, CA).
When is the first and last frost in Casa de Oro-Mount Helix?
There is no reliable frost date: a 32° night comes in about 73% of winters at El Cajon, CA, so most years bring a freeze but some pass without one.
What growing zone is Casa de Oro-Mount Helix in?
Zone 10b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 37°.
What is the best time of year to visit Casa de Oro-Mount Helix?
By one simple rule (highs of 62–84° and lows of 40° or more), January, February, March, April, May, June, October, November and December. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Casa de Oro-Mount Helix getting warmer?
Yes: 1991–2020 averaged 2.2° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 95% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Casa de Oro-Mount Helix.
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.