Photo: Allie_Caulfield · CC BY 2.0Arroyo Grande has some of the coolest summers among U.S. towns
Nights in January average 48°. By January nights alone, it runs milder than 95% of U.S. towns. Decade by decade the climate has edged up, 2.0° above 1901–2000. The outdoor season runs from March to November, with highs of 62–68°.
A year in Arroyo Grande at a glance
Each month’s typical high and low, and what it brings.
What stands out about Arroyo Grande’s climate
Compared with towns across the U.S., with Arroyo Grande’s place in California beside it.
What a year in Arroyo Grande feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
Frost is rare
Frost and day counts come from NOAA’s station at Morro Bay Fire Dept, CA, 22 miles from the town’s center, at about the same height.
The 2023 USDA map puts Arroyo Grande’s center in zone 10a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 32°. 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 15 inches of rain a year
January is the wettest month and July the driest. Rain falls on about 42 days a year. Snow is rare: about 0.1" in a normal year at Morro Bay Fire Dept, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Arroyo Grande
91% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from December through February.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Morro Bay Fire Dept, CA.
Living with Arroyo Grande’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 10a. Frost comes about 1 winter in 7, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: March, April, May, June, July, August, September, October and November. 7.2 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Arroyo Grande from natural hazards, river flooding is the largest share (72%). Normals are averages; the hazards page covers the extremes.
Natural hazards →Arroyo Grande and its neighbors
Pismo Beach has the coldest January nights next door (46°, 1° colder) and Pismo Beach the hottest July afternoons (68°, 3° 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 Arroyo Grande’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 |
|---|---|---|---|---|
| Arroyo Grande, CA | 48° | 65° | 15" | 0.1" |
| Port Angeles, WA | 37° | 69° | 28" | 0.4" |
| Makawao, HI | 53° | 75° | 23" | 0.0" |
| Coos Bay, OR | 40° | 66° | 61" | 0.2" |
| Nantucket, MA | 26° | 76° | 44" | 25" |
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 Arroyo Grande averaged 2.0° warmer than the 1900s. The biggest change is in January (+2.7°).
A bigger shift than in 89% 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 Arroyo Grande compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Arroyo Grande’s place among California’s.
Arroyo Grande weather by month
Highs, lows and precipitation from NOAA’s grid at Arroyo Grande’s center; snow, wet days and snow on the ground from Morro Bay Fire Dept, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 62° | 48° | 3.4" | 0.1" | 7 | 0 | 51° – 59° |
| February | 62° | 48° | 3.2" | 0.0" | 8 | 0 | 51° – 61° |
| March | 62° | 49° | 2.6" | 0.0" | 7 | 0 | 50° – 62° |
| April | 63° | 50° | 1.1" | 0.0" | 4 | 0 | 52° – 61° |
| May | 63° | 52° | 0.3" | 0.0" | 2 | 0 | 53° – 63° |
| June | 65° | 54° | 0.1" | 0.0" | 0 | 0 | 55° – 63° |
| July | 65° | 57° | 0.0" | 0.0" | 0 | 0 | 58° – 65° |
| August | 66° | 57° | 0.0" | 0.0" | 0 | 0 | 59° – 65° |
| September | 67° | 57° | 0.1" | 0.0" | 1 | 0 | 59° – 67° |
| October | 68° | 55° | 0.6" | 0.0" | 2 | 0 | 57° – 67° |
| November | 66° | 51° | 1.4" | 0.0" | 3 | 0 | 52° – 62° |
| December | 62° | 47° | 2.4" | 0.0" | 7 | 0 | 52° – 59° |
| Year | 64° | 52° | 15.2" | 0.1" | 42 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 50° to 62°. August is the most reliable, staying within 6°.
Where Arroyo Grande’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 Arroyo Grande’s center.
- Snow: Morro Bay Fire Dept, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Morro Bay Fire Dept, CA, 22 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 Arroyo Grande’s climate
What is the weather like in Arroyo Grande?
A typical July afternoon reaches 65°, a January night drops to 48°, and snow is almost unheard of. Milder January nights than 95% of U.S. towns; cooler July afternoons than all but 21 U.S. towns.
How cold does it get in Arroyo Grande in winter?
December nights average 47°. 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 Arroyo Grande get?
About 0.1 inches in a normal winter at Morro Bay Fire Dept, CA, so most winters see none.
How hot does it get in Arroyo Grande?
July, with a typical high of 65° and a low of 57°. About 1 days a year reach 90° (Morro Bay Fire Dept, CA).
When is the first and last frost in Arroyo Grande?
Most years have no frost at all: a 32° night comes in about 15% of winters at Morro Bay Fire Dept, CA, usually in December or January.
What growing zone is Arroyo Grande in?
Zone 10a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 32°.
What is the best time of year to visit Arroyo Grande?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, June, July, August, September, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Arroyo Grande getting warmer?
Yes: 1991–2020 averaged 2.0° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 89% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Arroyo Grande.
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.