Sunnyside, Washington climate: Normal weather by month, frost dates and records
Sunnyside's normal year runs from 22°F December nights to 88°F July afternoons, with 7.7 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.9°C, December lows of −5°C, July highs of 31°C, 194 mm of precipitation a year.
- NOAA stationSunnyside
- Station IDUSC00458207
- Location46.32°N 120.01°W
- Elevation747 ft (228 m)
- Population16,317
On October 23, the normal high in Sunnyside is 60°F and the normal low 33°F, and the chance of measurable rain or snow is 20%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Sunnyside.
- Jan 38° 23°
- Feb 45° 24°
- Mar 55° 30°
- Apr 63° 36°
- May 73° 44°
- Jun 79° 49°
- Jul 88° 54°
- Aug 87° 52°
- Sep 78° 45°
- Oct 64° 35°
- Nov 48° 27°
- Dec 37° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Sunnyside each month?
July is the warmest month, with normal highs of 88°F; December the coldest, with normal lows of 22°F. The most precipitation falls in December (1.18 in), the least in July (0.14 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 38°F | 23°F | 30.3°F | 0.98 | 9 | <1 | 26 | 9 h |
| February | 45°F | 24°F | 34.9°F | 0.65 | 6 | <1 | 22 | 10 h 20 min |
| March | 55°F | 30°F | 42.5°F | 0.54 | 6 | <1 | 15 | 11 h 50 min |
| April | 63°F | 36°F | 49.4°F | 0.61 | 6 | <1 | 6 | 13 h 30 min |
| May | 73°F | 44°F | 58.2°F | 0.75 | 6 | 3 | 1 | 15 h |
| June | 79°F | 49°F | 64.2°F | 0.59 | 4 | 5 | <1 | 15 h 50 min |
| July | 88°F | 54°F | 71.3°F | 0.14 | 2 | 18 | <1 | 15 h 30 min |
| August | 87°F | 52°F | 69.4°F | 0.26 | 2 | 15 | <1 | 14 h 10 min |
| September | 78°F | 45°F | 61.1°F | 0.36 | 3 | 5 | <1 | 12 h 40 min |
| October | 64°F | 35°F | 49.4°F | 0.74 | 6 | <1 | 7 | 11 h |
| November | 48°F | 27°F | 37.8°F | 0.85 | 8 | <1 | 20 | 9 h 30 min |
| December | 37°F | 22°F | 29.7°F | 1.18 | 9 | <1 | 26 | 8 h 40 min |
| Year (annual) | 63°F | 37°F | 49.9°F | 7.65 | 66 | 45 | 124 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 3°C | −5°C | −0.9°C | 25 mm |
| February | 7°C | −4°C | 1.6°C | 17 mm |
| March | 13°C | −1°C | 5.8°C | 14 mm |
| April | 17°C | 2°C | 9.7°C | 15 mm |
| May | 23°C | 7°C | 14.6°C | 19 mm |
| June | 26°C | 10°C | 17.9°C | 15 mm |
| July | 31°C | 12°C | 21.8°C | 4 mm |
| August | 30°C | 11°C | 20.8°C | 7 mm |
| September | 25°C | 7°C | 16.2°C | 9 mm |
| October | 18°C | 2°C | 9.7°C | 19 mm |
| November | 9°C | −3°C | 3.2°C | 22 mm |
| December | 3°C | −5°C | −1.3°C | 30 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Moxee City (10 mi E) (15 miles away), gets 10 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00458207; 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.
When is the best weather to visit Sunnyside?
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 USC00458207.
When is the last frost in Sunnyside?
In Sunnyside, the last spring frost (32°F) comes after May 1 in half of years and after May 18 in one year in ten; the first autumn frost comes before October 6 in half of years and before September 25 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
- May 11 year in 10 after May 18; 9 in 10 after April 16
- First autumn frost, half of years before
- October 61 year in 10 before September 25; 9 in 10 before October 22
NOAA puts the median frost-free season at 157 days, and the season without a hard freeze (28°F) at 187 days.
A hard freeze (28°F) comes after April 15 in half of springs and before October 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Sunnyside in zone 7b in ZIP code 98930, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Sunnyside's NOAA station is in zone 7b: the coldest night of a typical year reaches 7°F (17 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 USC00458207; 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 in Sunnyside?
In a normal year in Sunnyside, 45 days a year reach 90°F (7 of them 100°F or more), 124 nights fall to 32°F or colder and 66 days bring measurable precipitation.
- Days at 90°F or more
- 45a normal year
- Days at 100°F or more
- 7a normal year
- Nights at 32°F or colder
- 124a normal year
- Days that stay below freezing
- 16high of 32°F or less
- Days with 0.01 inch of precipitation
- 66a normal year
The highest temperature in this station's record (since 1894) is 112°F, on July 27, 1939; the lowest is −26°F, on January 21, 1930.
The wettest calendar year on that record is 1995, with 12.92 in; the snowiest season is 1955–56, with 33.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00458207; records: ACIS (NOAA Regional Climate Centers), station USC00458207. Records use complete months only; a month missing more than three days is left out.
How sunny is Sunnyside?
Over a year 77% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Sunnyside, 4.1 kWh per square metre a day. July is the sunniest month (90%) and December the cloudiest (56%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 59% | 1.3 |
| February | 67% | 2.3 |
| March | 67% | 3.4 |
| April | 73% | 5.0 |
| May | 75% | 6.0 |
| June | 79% | 6.8 |
| July | 90% | 7.5 |
| August | 89% | 6.3 |
| September | 84% | 4.6 |
| October | 74% | 2.8 |
| November | 63% | 1.5 |
| December | 56% | 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 much heating and cooling does Sunnyside need?
A normal year in Sunnyside brings 5,994 heating degree days, 12% more than the median U.S. place (5,373), and 499 cooling degree days, 45% 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 2,448 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,076 | 0 |
| February | 844 | 0 |
| March | 696 | 0 |
| April | 468 | 1 |
| May | 235 | 25 |
| June | 94 | 69 |
| July | 16 | 211 |
| August | 26 | 161 |
| September | 149 | 32 |
| October | 484 | 0 |
| November | 815 | 0 |
| December | 1,093 | 0 |
| Year (annual) | 5,994 | 499 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00458207. 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.
How does Sunnyside's climate compare?
Sunnyside is warmer than 37 of the other 95 places with their own NOAA record in Washington, and wetter than 4. Across the 7,247 U.S. stations with normals, its annual mean of 49.9°F is warmer than 40%.
In the Köppen classification computed from these normals, Sunnyside 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 Sunnyside share this climate record?
4 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.
- Grandview, WA11,599 people · 7 mi SE
- Granger, WA3,789 people · 9 mi W
- Mabton, WA1,960 people · 8 mi S
- Outlook, WA504 people · 4 mi W
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Sunnyside's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Sunnyside. This page uses Sunnyside; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Sunnyside #2 USC00458211 | 2 mi NW | 805 ft | 50.2°F | 24°F | 88°F | 8.3 | – | April 30 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Sunnyside's climate
What is the coldest month in Sunnyside?
December, with a normal high of 37°F and a normal low of 22°F. The warmest is July (88°F by day, 54°F at night).
Does it snow in Sunnyside?
Yes. NOAA publishes no 1991-2020 snowfall normal for Sunnyside's NOAA station; the nearest record that keeps one, Moxee City (10 mi E) (15 miles away), records 10 inches of snow in a normal year.
What is the rainiest month in Sunnyside?
December, with 1.18 in of precipitation in a normal year; the driest is July with 0.14 in.
What plant hardiness zone is Sunnyside in?
The USDA's 2023 map puts Sunnyside in zone 7b in ZIP code 98930, the nearest ZIP area. By the same method at Sunnyside's NOAA station, the coldest night of a typical year reaches 7°F (17 years, 1991-2020): zone 7b.
How late can frost come in Sunnyside?
In half of years the last 32°F night comes after May 1; in one year in ten it comes after May 18. Waiting until May 18 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Washington climateThe statewide normals and every place in the state
- Moxee City (10 mi E), WA15 miles from this station, 50.2°F a year
- Prosser, WA15 miles from this station, 53.0°F a year
- Wapato, WA21 miles from this station, 52.3°F a year
- Priest Rapids Dam, WA23 miles from this station, 56.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made