Castle Rock sits near the bottom of U.S. towns for July heat
Midwinter brings lows of about 35°. Seasons differ by 45°, from the coldest nights to the warmest afternoons. By January nights alone, it runs milder than 79% of U.S. towns. From May to October, highs of 62–80° make it easy to spend the day outdoors.
A year in Castle Rock at a glance
Each month’s typical high and low, and what it brings.
What stands out about Castle Rock’s climate
Compared with towns across the U.S., with Castle Rock’s place in Washington beside it.
What a year in Castle Rock feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 210 frost-free days a year
In half of years the last 32° night comes by April 8 and the first by November 5. Frost and day counts come from NOAA’s station at Longview, WA, 8 miles from the town’s center, at about the same height.
The 2023 USDA map puts Castle Rock’s center in zone 8b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 18°. 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 2 inches of snow a winter
Snow, measured at Clatskanie, OR, falls mostly in December. Precipitation (rain plus melted snow) adds up to 48 inches a year; December is the wettest month and July the driest. Rain or snow falls on about 192 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Castle Rock
95% of the work is heating, so the furnace matters far more than the air conditioner. 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 Longview, WA.
Living with Castle Rock’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
210 frost-free days in zone 8b. The last frost comes by Apr 8 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 5.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 2.8 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Castle Rock from natural hazards, river flooding is the largest share (44%); heat waves, cold waves, winter storms and ice storms together are 6%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Castle Rock and similar climates
TownRatings has no climate map of the towns around Castle Rock yet.
Climates most like Castle Rock’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 |
|---|---|---|---|---|
| Castle Rock, WA | 35° | 79° | 48" | 2.3" |
| Cottage Grove, OR | 35° | 82° | 47" | 2.7" |
| Ben Lomond, CA | 40° | 79° | 43" | 0.0" |
| Swannanoa, NC | 27° | 83° | 48" | 2.1" |
| Brigantine, NJ | 28° | 83° | 45" | 10" |
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 Castle Rock averaged 1.3° warmer than the 1900s. The biggest change is in January (+2.8°).
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 Castle Rock compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Castle Rock’s place among Washington’s.
Castle Rock weather by month
Highs, lows and precipitation from NOAA’s grid at Castle Rock’s center; snow, wet days and snow on the ground from Clatskanie, OR. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 47° | 35° | 6.6" | 0.5" | 22 | 1 | 34° – 45° |
| February | 51° | 35° | 4.7" | 0.7" | 19 | 0 | 36° – 49° |
| March | 56° | 37° | 5.0" | 0.2" | 22 | 0 | 43° – 51° |
| April | 61° | 40° | 4.1" | 0.0" | 20 | 0 | 46° – 55° |
| May | 68° | 45° | 2.9" | 0.0" | 14 | 0 | 52° – 60° |
| June | 72° | 49° | 2.0" | 0.0" | 12 | 0 | 58° – 66° |
| July | 79° | 53° | 0.6" | 0.0" | 6 | 0 | 62° – 69° |
| August | 80° | 52° | 0.9" | 0.0" | 5 | 0 | 63° – 69° |
| September | 74° | 48° | 2.1" | 0.0" | 9 | 0 | 58° – 64° |
| October | 62° | 43° | 4.4" | 0.0" | 18 | 0 | 48° – 57° |
| November | 52° | 38° | 7.2" | 0.1" | 23 | 0 | 40° – 49° |
| December | 45° | 34° | 7.4" | 0.8" | 23 | 1 | 35° – 43° |
| Year | 62° | 42° | 47.8" | 2.3" | 192 | 2 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 36° to 49°. August is the most reliable, staying within 6°.
Where Castle Rock’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 Castle Rock’s center.
- Snow: Clatskanie, OR.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Longview, WA, 8 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 Castle Rock’s climate
What is the weather like in Castle Rock?
A typical July afternoon reaches 79°, a January night drops to 35°, and about 2 inches of snow falls in a normal winter. Milder January nights than 79% of U.S. towns; cooler July afternoons than 95% of U.S. towns.
How cold does it get in Castle Rock in winter?
December nights average 34°. About 41 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 35°.
How much snow does Castle Rock get?
About 2.3 inches in a normal winter at Clatskanie, OR, most of it in December, with snow on the ground about 2 days a year.
How hot does it get in Castle Rock?
July, with a typical high of 79° and a low of 53°. About 10 days a year reach 90° (Longview, WA).
When is the first and last frost in Castle Rock?
In half of years the last spring frost (32°) comes by April 8 and the first fall frost by November 5, about 210 frost-free days, at Longview, WA.
What growing zone is Castle Rock in?
Zone 8b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 18°.
What is the best time of year to visit Castle Rock?
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 Castle Rock 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 Castle Rock.
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.