Photo: Ellin Beltz · Public domainFew U.S. towns have cooler summers than Rio Dell
In January the night’s low is typically 41°. Winters are mild: January nights here are milder than in 90% of U.S. towns. Compared with 1901–2000, the average now sits 1.5° higher. Keep the boiler serviced for the months from December to February, which average under 50°.
A year in Rio Dell at a glance
Each month’s typical high and low, and what it brings.
What stands out about Rio Dell’s climate
Compared with towns across the U.S., with Rio Dell’s place in California beside it.
What a year in Rio Dell 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 Scotia, CA, 1.1 miles from the town’s center, at about the same height.
The 2023 USDA map puts Rio Dell’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 27°. 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 49 inches of rain a year
December is the wettest month and July the driest. Rain falls on about 112 days a year. Snow is rare: about 0.7" in a normal year at Grizzly Creek Sp, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Rio Dell
98% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from November 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 Scotia, CA.
Living with Rio Dell’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 9b. Frost comes about 8 winters in 10, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 0.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Rio Dell from natural hazards, river flooding is the largest share (63%). Normals are averages; the hazards page covers the extremes.
Natural hazards →Rio Dell and similar climates
TownRatings has no climate map of the towns around Rio Dell yet.
Climates most like Rio Dell’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 |
|---|---|---|---|---|
| Rio Dell, CA | 41° | 74° | 49" | 0.7" |
| Lake Stevens, WA | 35° | 74° | 50" | 3.0" |
| Happy Valley, OR | 36° | 80° | 49" | 3.6" |
| Black Mountain, NC | 27° | 82° | 57" | 2.1" |
| Nantucket, MA | 26° | 76° | 44" | 25" |
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 Rio Dell averaged 1.5° warmer than the 1900s. The biggest change is in January (+2.4°).
A bigger shift than in 57% 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 Rio Dell compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Rio Dell’s place among California’s.
Rio Dell weather by month
Highs, lows and precipitation from NOAA’s grid at Rio Dell’s center; snow, wet days and snow on the ground from Grizzly Creek Sp, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 54° | 41° | 8.7" | 0.1" | 16 | 0 | 44° – 54° |
| February | 56° | 41° | 7.8" | 0.1" | 14 | 0 | 43° – 53° |
| March | 58° | 42° | 7.3" | 0.3" | 15 | 0 | 46° – 54° |
| April | 61° | 44° | 4.1" | 0.0" | 13 | 0 | 50° – 57° |
| May | 66° | 48° | 2.0" | 0.0" | 9 | 0 | 53° – 61° |
| June | 69° | 51° | 0.6" | 0.0" | 5 | 0 | 56° – 63° |
| July | 74° | 54° | 0.1" | 0.0" | 2 | 0 | 62° – 67° |
| August | 76° | 54° | 0.1" | 0.0" | 2 | 0 | 63° – 67° |
| September | 75° | 52° | 0.5" | 0.0" | 2 | 0 | 60° – 68° |
| October | 68° | 47° | 2.5" | 0.0" | 6 | 0 | 55° – 62° |
| November | 58° | 43° | 5.5" | 0.0" | 13 | 0 | 44° – 54° |
| December | 53° | 40° | 9.9" | 0.2" | 15 | 0 | 43° – 50° |
| Year | 64° | 46° | 49.2" | 0.7" | 112 | 0 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 44° to 54°. August is the most reliable, staying within 5°.
Where Rio Dell’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 Rio Dell’s center.
- Snow: Grizzly Creek Sp, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Scotia, CA, 1.1 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 Rio Dell’s climate
What is the weather like in Rio Dell?
A typical July afternoon reaches 74°, a January night drops to 41°, and snow is almost unheard of. Milder January nights than 90% of U.S. towns; cooler July afternoons than all but 179 U.S. towns.
How cold does it get in Rio Dell in winter?
December nights average 40°. About 6 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 43°.
How much snow does Rio Dell get?
About 0.7 inches in a normal winter at Grizzly Creek Sp, CA, so most winters see none.
How hot does it get in Rio Dell?
July, with a typical high of 74° and a low of 54°. About 2 days a year reach 90° (Scotia, CA).
When is the first and last frost in Rio Dell?
There is no reliable frost date: a 32° night comes in about 84% of winters at Scotia, CA, so most years bring a freeze but some pass without one.
What growing zone is Rio Dell in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 27°.
What is the best time of year to visit Rio Dell?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Rio Dell getting warmer?
Yes: 1991–2020 averaged 1.5° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 57% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Rio Dell.
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.