Photo: Roger Puta · Public domainPortola’s winters are milder but snowier than most of the U.S.
A typical July afternoon reaches 86°, a January night drops to 22°, and about 38 inches of snow falls in a normal winter.
A year in Portola at a glance
Each month’s typical high and low, and what it brings.
What stands out about Portola’s climate
Compared with towns across the U.S., with Portola’s place in California beside it.
What a year in Portola feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 91 frost-free days a year
In half of years the last 32° night comes by June 11 and the first by September 10. Frost and day counts come from NOAA’s station at Portola, CA, 1.1 miles from the town’s center, 160 ft lower.
The 2023 USDA map puts Portola’s center in zone 6b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −4°. 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 38 inches of snow a winter
Snow, measured at Portola, CA, falls mostly in January. Precipitation (rain plus melted snow) adds up to 24 inches a year; December is the wettest month and August the driest. Rain or snow falls on about 62 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Portola
98% 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 Portola, CA.
Living with Portola’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
91 frost-free days in zone 6b. The last frost comes by Jun 11 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 10.
Months with highs of 62–84° and lows of 40° or more: June and September. 11 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Portola from natural hazards, river flooding is the largest share (47%). Normals are averages; the hazards page covers the extremes.
Natural hazards →Portola and its neighbors
Every town next door is within a degree of Portola in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Portola’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 |
|---|---|---|---|---|
| Portola, CA | 22° | 86° | 24" | 38" |
| Spokane Valley, WA | 25° | 85° | 20" | 45" |
| Dakota Ridge, CO | 19° | 87° | 18" | 34" |
| Moscow, ID | 25° | 84° | 25" | 51" |
| Hastings, NE | 15° | 87° | 27" | 29" |
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 Portola averaged 1.4° warmer than the 1900s. The biggest change is in January (+2.4°).
A bigger shift than in 53% 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 Portola compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Portola’s place among California’s.
Portola weather by month
Highs, lows and precipitation from NOAA’s grid at Portola’s center; snow, wet days and snow on the ground from Portola, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 43° | 22° | 4.2" | 11.7" | 9 | 9 | 23° – 39° |
| February | 47° | 24° | 3.8" | 7.6" | 9 | 6 | 29° – 43° |
| March | 52° | 27° | 3.5" | 6.4" | 8 | 5 | 32° – 46° |
| April | 58° | 31° | 1.7" | 1.8" | 6 | 1 | 39° – 49° |
| May | 67° | 37° | 1.3" | 0.2" | 6 | 0 | 44° – 58° |
| June | 77° | 42° | 0.6" | 0.0" | 3 | 0 | 55° – 65° |
| July | 86° | 48° | 0.2" | 0.0" | 1 | 0 | 62° – 72° |
| August | 85° | 45° | 0.2" | 0.0" | 1 | 0 | 62° – 69° |
| September | 79° | 40° | 0.4" | 0.1" | 2 | 0 | 56° – 63° |
| October | 66° | 32° | 1.2" | 0.4" | 4 | 0 | 45° – 53° |
| November | 52° | 26° | 2.1" | 2.4" | 6 | 1 | 30° – 44° |
| December | 42° | 22° | 4.3" | 7.2" | 8 | 6 | 26° – 37° |
| Year | 63° | 33° | 23.5" | 37.8" | 62 | 29 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 23° to 39°. August is the most reliable, staying within 7°.
Where Portola’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 Portola’s center.
- Snow: Portola, CA (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Portola, CA, 1.1 miles from the town’s center, 160 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 Portola’s climate
What is the weather like in Portola?
A typical July afternoon reaches 86°, a January night drops to 22°, and about 38 inches of snow falls in a normal winter. Milder January nights than 50% of U.S. towns; hotter July afternoons than 58% of U.S. towns.
How cold does it get in Portola in winter?
December nights average 22°. About 205 nights a year reach 32° or below and 2 reach 0° or below. In the coldest December of the last 30 years the month averaged 26°.
How much snow does Portola get?
About 38 inches in a normal winter at Portola, CA, most of it in January, with snow on the ground about 29 days a year.
How hot does it get in Portola?
July, with a typical high of 86° and a low of 48°. About 22 days a year reach 90° (Portola, CA).
When is the first and last frost in Portola?
In half of years the last spring frost (32°) comes by June 11 and the first fall frost by September 10, about 91 frost-free days, at Portola, CA.
What growing zone is Portola in?
Zone 6b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −4°.
What is the best time of year to visit Portola?
By one simple rule (highs of 62–84° and lows of 40° or more), June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Portola getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 53% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Portola.
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.