Ice Harbor Dam, Washington climate: Climate normals at a NOAA weather station
Ice Harbor Dam's normal year runs from 29°F January nights to 89°F July afternoons, with 11.1 inches of precipitation and 2 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.2°C, January lows of −2°C, July highs of 32°C, 282 mm of precipitation a year.
- NOAA stationIce Harbor Dam
- Station IDUSC00453883
- Location46.24°N 118.88°W
- Elevation368 ft (112 m)
On October 23, the normal high in Ice Harbor Dam is 62°F and the normal low 40°F, and the chance of measurable rain or snow is 30%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Ice Harbor Dam.
- Jan 42° 29°
- Feb 48° 30°
- Mar 58° 35°
- Apr 65° 41°
- May 74° 48°
- Jun 80° 54°
- Jul 89° 61°
- Aug 89° 59°
- Sep 80° 51°
- Oct 66° 42°
- Nov 51° 35°
- Dec 42° 29°
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 Ice Harbor Dam each month?
July is the warmest month, with normal highs of 89°F; January the coldest, with normal lows of 29°F. The most precipitation falls in December (1.43 in), the least in July (0.26 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 42°F | 29°F | 35.4°F | 1.42 | 0.2 | 14 | <1 | 19 | 9 h |
| February | 48°F | 30°F | 38.9°F | 1.04 | 0.2 | 10 | <1 | 17 | 10 h 20 min |
| March | 58°F | 35°F | 46.2°F | 1.02 | 0.1 | 10 | <1 | 10 | 11 h 50 min |
| April | 65°F | 41°F | 52.9°F | 0.98 | 0.0 | 9 | <1 | 2 | 13 h 30 min |
| May | 74°F | 48°F | 60.9°F | 1.15 | 0.0 | 8 | 1 | <1 | 15 h |
| June | 80°F | 54°F | 67.2°F | 0.85 | 0.0 | 6 | 3 | <1 | 15 h 50 min |
| July | 89°F | 61°F | 74.8°F | 0.26 | 0.0 | 3 | 15 | <1 | 15 h 30 min |
| August | 89°F | 59°F | 74.0°F | 0.30 | 0.0 | 2 | 14 | <1 | 14 h 10 min |
| September | 80°F | 51°F | 65.6°F | 0.39 | 0.0 | 4 | 3 | <1 | 12 h 40 min |
| October | 66°F | 42°F | 53.9°F | 1.02 | 0.0 | 8 | <1 | 3 | 11 h |
| November | 51°F | 35°F | 42.9°F | 1.26 | 0.1 | 12 | <1 | 12 | 9 h 30 min |
| December | 42°F | 29°F | 35.6°F | 1.43 | 1.4 | 13 | <1 | 20 | 8 h 40 min |
| Year (annual) | 65°F | 43°F | 54.0°F | 11.12 | 2.0 | 97 | 37 | 84 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 5°C | −2°C | 1.9°C | 36 mm | 1 cm |
| February | 9°C | −1°C | 3.8°C | 26 mm | 1 cm |
| March | 14°C | 2°C | 7.9°C | 26 mm | 0 cm |
| April | 18°C | 5°C | 11.6°C | 25 mm | 0 cm |
| May | 23°C | 9°C | 16.1°C | 29 mm | 0 cm |
| June | 27°C | 12°C | 19.6°C | 22 mm | 0 cm |
| July | 32°C | 16°C | 23.8°C | 7 mm | 0 cm |
| August | 31°C | 15°C | 23.3°C | 8 mm | 0 cm |
| September | 27°C | 11°C | 18.7°C | 10 mm | 0 cm |
| October | 19°C | 6°C | 12.2°C | 26 mm | 0 cm |
| November | 11°C | 1°C | 6.1°C | 32 mm | 0 cm |
| December | 6°C | −2°C | 2.0°C | 36 mm | 4 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00453883; 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 Ice Harbor Dam?
Normal highs sit between 65°F and 85°F in April, May, June, September and October. Of those, September has the fewest days with rain (4).
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 USC00453883.
When is the last frost at Ice Harbor Dam?
In Ice Harbor Dam, the last spring frost (32°F) comes after April 7 in half of years and after April 30 in one year in ten; the first autumn frost comes before October 22 in half of years and before October 6 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 71 year in 10 after April 30; 9 in 10 after March 20
- First autumn frost, half of years before
- October 221 year in 10 before October 6; 9 in 10 before November 9
NOAA puts the median frost-free season at 199 days, and the season without a hard freeze (28°F) at 230 days.
A hard freeze (28°F) comes after March 18 in half of springs and before November 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Ice Harbor Dam in zone 7a in ZIP code 99323, 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 7b: the coldest night of a typical year reaches 6°F (22 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Washington · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00453883; 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 Ice Harbor Dam?
In a normal year in Ice Harbor Dam, 37 days a year reach 90°F (3 of them 100°F or more), 84 nights fall to 32°F or colder and 97 days bring measurable precipitation.
- Days at 90°F or more
- 37a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 84a normal year
- Days that stay below freezing
- 12high of 32°F or less
- Days with 0.01 inch of precipitation
- 97a normal year
- Days with 1 inch of snow or more
- 2a normal year
The highest temperature in this station's record (since 1957) is 118°F, on August 5, 1961; the lowest is −14°F, on February 4, 1996.
The wettest calendar year on that record is 1996, with 17.26 in; the snowiest season is 1968–69, with 30.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00453883; records: ACIS (NOAA Regional Climate Centers), station USC00453883. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Ice Harbor Dam?
Over a year 81% of the sunlight that would reach the ground under clear skies gets through the clouds at Ice Harbor Dam, 4.2 kWh per square metre a day. July is the sunniest month (94%) and December the cloudiest (55%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 56% | 1.2 |
| February | 69% | 2.3 |
| March | 72% | 3.6 |
| April | 79% | 5.4 |
| May | 81% | 6.5 |
| June | 85% | 7.2 |
| July | 94% | 7.7 |
| August | 92% | 6.4 |
| September | 87% | 4.7 |
| October | 79% | 3.0 |
| November | 65% | 1.6 |
| December | 55% | 1.0 |
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 Ice Harbor Dam record?
A normal year at Ice Harbor Dam brings 4,780 heating degree days, 11% fewer than the median U.S. place (5,373), and 811 cooling degree days, 11% 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 3,172 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 919 | 0 |
| February | 731 | 0 |
| March | 581 | 0 |
| April | 363 | 1 |
| May | 158 | 29 |
| June | 39 | 104 |
| July | 2 | 308 |
| August | 4 | 283 |
| September | 63 | 82 |
| October | 347 | 4 |
| November | 663 | 0 |
| December | 910 | 0 |
| Year (annual) | 4,780 | 811 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00453883. 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 Ice Harbor Dam been warmer than normal?
2021 averaged 56.0°F, 2.0°F above the 1991-2020 normal of 54.0°F.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 56.0°F | +2.0°F | 7.59 | – |
Over 42 complete years from 1958 to 2021, the station's annual mean temperature rose at a fitted 0.3°F per century (+0.01°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00453883; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Ice Harbor Dam's climate compare?
Ice Harbor Dam is warmer than 93 of the 96 places with their own NOAA record in Washington, and wetter than 19. Across the 7,247 U.S. stations with normals, its annual mean of 54.0°F is warmer than 57%.
In the Köppen classification computed from these normals, Ice Harbor 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 Ice Harbor Dam share this climate record?
Wallula has no NOAA station with 1991-2020 normals of its 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.
- Wallula, WA127 people · 11 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 Ice Harbor Dam's climate
What is the coldest month at Ice Harbor Dam?
January, with a normal high of 42°F and a normal low of 29°F. The warmest is July (89°F by day, 61°F at night).
Does it snow at Ice Harbor Dam?
Yes: 2 inches in a normal year, falling on 2 days with 0.1 inch or more, the most in December (1.4 inches).
What is the rainiest month at Ice Harbor Dam?
December, with 1.43 in of precipitation in a normal year; the driest is July with 0.26 in.
What plant hardiness zone is Ice Harbor Dam in?
The USDA's 2023 map puts Ice Harbor Dam in zone 7a in ZIP code 99323, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches 6°F (22 years, 1991-2020): zone 7b.
How late can frost come at Ice Harbor Dam?
In half of years the last 32°F night comes after April 7; in one year in ten it comes after April 30. Waiting until April 30 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Washington climateThe statewide normals and every place in the state
- Kennewick, WA11 miles from this station, 55.0°F a year
- Pasco, WA11 miles from this station, 53.3°F a year
- Sagemoor, WA14 miles from this station, 52.0°F a year
- Eltopia (8 mi WSW), WA17 miles from this station, 51.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made