Chief Joseph Dam, Washington climate: Climate normals at a NOAA weather station
Chief Joseph Dam's normal year runs from 23°F January nights to 91°F July afternoons, with 10.8 inches of precipitation and 28 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.6°C, January lows of −5°C, July highs of 33°C, 274 mm of precipitation a year.
- NOAA stationChief Joseph Dam
- Station IDUSC00451400
- Location48.00°N 119.65°W
- Elevation834 ft (254 m)
On October 23, the normal high in Chief Joseph Dam is 58°F and the normal low 36°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Chief Joseph Dam.
- Jan 34° 23°
- Feb 42° 25°
- Mar 54° 32°
- Apr 64° 38°
- May 74° 46°
- Jun 81° 52°
- Jul 91° 58°
- Aug 90° 58°
- Sep 80° 49°
- Oct 63° 38°
- Nov 45° 30°
- Dec 35° 23°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at Chief Joseph Dam each month?
July is the warmest month, with normal highs of 91°F; January the coldest, with normal lows of 23°F. The most precipitation falls in December (2.01 in), the least in August (0.22 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 34°F | 23°F | 28.5°F | 1.42 | 8.5 | 10 | <1 | 28 | 8 h 50 min |
| February | 42°F | 25°F | 33.3°F | 0.95 | 3.1 | 7 | <1 | 23 | 10 h 10 min |
| March | 54°F | 32°F | 42.9°F | 1.05 | 0.6 | 6 | <1 | 17 | 11 h 50 min |
| April | 64°F | 38°F | 51.1°F | 0.62 | 0.0 | 5 | <1 | 6 | 13 h 40 min |
| May | 74°F | 46°F | 59.9°F | 0.92 | 0.0 | 6 | 2 | 1 | 15 h 10 min |
| June | 81°F | 52°F | 66.4°F | 0.81 | 0.0 | 5 | 5 | <1 | 16 h |
| July | 91°F | 58°F | 74.6°F | 0.48 | 0.0 | 3 | 19 | <1 | 15 h 40 min |
| August | 90°F | 58°F | 73.9°F | 0.22 | 0.0 | 2 | 18 | <1 | 14 h 20 min |
| September | 80°F | 49°F | 64.5°F | 0.35 | 0.0 | 3 | 5 | <1 | 12 h 40 min |
| October | 63°F | 38°F | 50.4°F | 0.78 | 0.0 | 5 | <1 | 7 | 11 h |
| November | 45°F | 30°F | 37.4°F | 1.16 | 2.2 | 9 | <1 | 19 | 9 h 20 min |
| December | 35°F | 23°F | 28.9°F | 2.01 | 13.5 | 11 | <1 | 28 | 8 h 20 min |
| Year (annual) | 63°F | 39°F | 51.0°F | 10.77 | 27.9 | 72 | 48 | 128 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 1°C | −5°C | −1.9°C | 36 mm | 22 cm |
| February | 5°C | −4°C | 0.7°C | 24 mm | 8 cm |
| March | 12°C | 0°C | 6.1°C | 27 mm | 2 cm |
| April | 18°C | 3°C | 10.6°C | 16 mm | 0 cm |
| May | 23°C | 8°C | 15.5°C | 23 mm | 0 cm |
| June | 27°C | 11°C | 19.1°C | 21 mm | 0 cm |
| July | 33°C | 15°C | 23.7°C | 12 mm | 0 cm |
| August | 32°C | 14°C | 23.3°C | 6 mm | 0 cm |
| September | 27°C | 10°C | 18.1°C | 9 mm | 0 cm |
| October | 17°C | 3°C | 10.2°C | 20 mm | 0 cm |
| November | 7°C | −1°C | 3.0°C | 29 mm | 6 cm |
| December | 1°C | −5°C | −1.7°C | 51 mm | 34 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00451400; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
Which months are mildest at Chief Joseph Dam?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (3).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00451400.
When is the last frost at Chief Joseph Dam?
In Chief Joseph Dam, the last spring frost (32°F) comes after April 26 in half of years and after May 13 in one year in ten; the first autumn frost comes before October 11 in half of years and before September 30 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 261 year in 10 after May 13; 9 in 10 after April 9
- First autumn frost, half of years before
- October 111 year in 10 before September 30; 9 in 10 before October 27
NOAA puts the median frost-free season at 167 days, and the season without a hard freeze (28°F) at 196 days.
A hard freeze (28°F) comes after April 9 in half of springs and before October 23 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Chief Joseph Dam in zone 7a in ZIP code 98813, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 7a: the coldest night of a typical year reaches 1°F (23 complete years).
Frost dates for every NOAA station in Washington · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00451400; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get at Chief Joseph Dam?
In a normal year in Chief Joseph Dam, 48 days a year reach 90°F (10 of them 100°F or more), 128 nights fall to 32°F or colder and 72 days bring measurable precipitation.
- Days at 90°F or more
- 48a normal year
- Days at 100°F or more
- 10a normal year
- Nights at 32°F or colder
- 128a normal year
- Days that stay below freezing
- 26high of 32°F or less
- Days with 0.01 inch of precipitation
- 72a normal year
- Days with 1 inch of snow or more
- 11a normal year
The highest temperature in this station's record (since 1949) is 113°F, on June 28, 2015; the lowest is −19°F, on January 30, 1950.
The wettest calendar year on that record is 1983, with 21.57 in; the snowiest season is 1996–97, with 66.4 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00451400; records: ACIS (NOAA Regional Climate Centers), station USC00451400. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Chief Joseph Dam?
Over a year 80% of the sunlight that would reach the ground under clear skies gets through the clouds at Chief Joseph Dam, 4.1 kWh per square metre a day. July is the sunniest month (92%) and December the cloudiest (53%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 55% | 1.1 |
| February | 69% | 2.3 |
| March | 71% | 3.5 |
| April | 78% | 5.2 |
| May | 80% | 6.4 |
| June | 81% | 7.0 |
| July | 92% | 7.5 |
| August | 91% | 6.3 |
| September | 86% | 4.6 |
| October | 78% | 2.9 |
| November | 64% | 1.5 |
| December | 53% | 0.9 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How many heating and cooling degree days does Chief Joseph Dam record?
A normal year at Chief Joseph Dam brings 5,874 heating degree days, 9% more than the median U.S. place (5,373), and 794 cooling degree days, 12% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,942 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,131 | 0 |
| February | 889 | 0 |
| March | 687 | 0 |
| April | 418 | 1 |
| May | 188 | 28 |
| June | 57 | 98 |
| July | 8 | 305 |
| August | 7 | 284 |
| September | 92 | 77 |
| October | 453 | 2 |
| November | 827 | 0 |
| December | 1,119 | 0 |
| Year (annual) | 5,874 | 794 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00451400. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Have recent years at Chief Joseph Dam been warmer than normal?
Over 48 complete years from 1952 to 2019, the station's annual mean temperature rose at a fitted 2.7°F per century (+0.15°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Chief Joseph Dam's climate compare?
Chief Joseph Dam is warmer than 60 of the 96 places with their own NOAA record in Washington, and wetter than 15. Across the 7,247 U.S. stations with normals, its annual mean of 51.0°F is warmer than 45%.
In the Köppen classification computed from these normals, Chief Joseph Dam is BSk: cold semi-arid steppe. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Chief Joseph Dam share this climate record?
3 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Bridgeport, WA2,261 people · 1 mi NW
- Brewster, WA2,090 people · 9 mi NW
- Mansfield, WA340 people · 13 mi S
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Chief Joseph Dam's climate
What is the coldest month at Chief Joseph Dam?
January, with a normal high of 34°F and a normal low of 23°F. The warmest is July (91°F by day, 58°F at night).
Does it snow at Chief Joseph Dam?
Yes: 28 inches in a normal year, falling on 17 days with 0.1 inch or more, the most in December (13.5 inches).
What is the rainiest month at Chief Joseph Dam?
December, with 2.01 in of precipitation in a normal year; the driest is August with 0.22 in.
What plant hardiness zone is Chief Joseph Dam in?
The USDA's 2023 map puts Chief Joseph Dam in zone 7a in ZIP code 98813, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches 1°F (23 years, 1991-2020): zone 7a.
How late can frost come at Chief Joseph Dam?
In half of years the last 32°F night comes after April 26; in one year in ten it comes after May 13. Waiting until May 13 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Washington climateThe statewide normals and every place in the state
- Methow, WA18 miles from this station, 50.0°F a year
- Chelan, WA20 miles from this station, 50.1°F a year
- Coulee Dam, WA30 miles from this station, 49.9°F a year
- Waterville, WA31 miles from this station, 45.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made