Dayton, Washington climate: Normal weather by month, frost dates and records
Dayton's normal year runs from 27°F December nights to 88°F July afternoons, with 18.8 inches of precipitation and 16 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.6°C, December lows of −3°C, July highs of 31°C, 477 mm of precipitation a year.
- NOAA stationDayton (1 mi WSW)
- Station IDUSC00452030
- Location46.32°N 118.00°W
- Elevation1,557 ft (475 m)
- Population2,471
On October 23, the normal high in Dayton is 59°F and the normal low 36°F, and the chance of measurable rain or snow is 35%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Dayton.
- Jan 42° 26°
- Feb 46° 28°
- Mar 54° 33°
- Apr 61° 38°
- May 70° 45°
- Jun 77° 50°
- Jul 88° 55°
- Aug 87° 54°
- Sep 77° 47°
- Oct 63° 38°
- Nov 49° 31°
- Dec 41° 27°
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 Dayton each month?
July is the warmest month, with normal highs of 88°F; December the coldest, with normal lows of 27°F. The most precipitation falls in November (2.43 in), the least in July (0.39 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 42°F | 26°F | 34.0°F | 2.08 | 6.3 | 14 | <1 | 23 | 9 h |
| February | 46°F | 28°F | 37.2°F | 1.72 | 1.9 | 12 | <1 | 19 | 10 h 20 min |
| March | 54°F | 33°F | 43.4°F | 2.24 | 1.0 | 13 | <1 | 13 | 11 h 50 min |
| April | 61°F | 38°F | 49.4°F | 1.86 | 0.1 | 12 | <1 | 6 | 13 h 30 min |
| May | 70°F | 45°F | 57.2°F | 1.80 | 0.0 | 10 | 1 | 2 | 15 h |
| June | 77°F | 50°F | 63.4°F | 1.24 | 0.0 | 7 | 2 | 1 | 15 h 50 min |
| July | 88°F | 55°F | 71.3°F | 0.39 | 0.0 | 3 | 13 | <1 | 15 h 30 min |
| August | 87°F | 54°F | 70.5°F | 0.45 | 0.0 | 3 | 12 | 1 | 14 h 10 min |
| September | 77°F | 47°F | 62.2°F | 0.73 | 0.0 | 5 | 3 | 2 | 12 h 40 min |
| October | 63°F | 38°F | 50.4°F | 1.54 | 0.1 | 10 | <1 | 6 | 11 h |
| November | 49°F | 31°F | 40.2°F | 2.43 | 1.2 | 14 | <1 | 16 | 9 h 30 min |
| December | 41°F | 27°F | 33.6°F | 2.31 | 5.2 | 14 | <1 | 24 | 8 h 40 min |
| Year (annual) | 63°F | 39°F | 51.1°F | 18.79 | 15.8 | 117 | 31 | 113 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 5°C | −3°C | 1.1°C | 53 mm | 16 cm |
| February | 8°C | −2°C | 2.9°C | 44 mm | 5 cm |
| March | 12°C | 1°C | 6.3°C | 57 mm | 3 cm |
| April | 16°C | 3°C | 9.7°C | 47 mm | 0 cm |
| May | 21°C | 7°C | 14.0°C | 46 mm | 0 cm |
| June | 25°C | 10°C | 17.4°C | 31 mm | 0 cm |
| July | 31°C | 13°C | 21.8°C | 10 mm | 0 cm |
| August | 30°C | 12°C | 21.4°C | 11 mm | 0 cm |
| September | 25°C | 8°C | 16.8°C | 19 mm | 0 cm |
| October | 17°C | 3°C | 10.2°C | 39 mm | 0 cm |
| November | 10°C | −1°C | 4.6°C | 62 mm | 3 cm |
| December | 5°C | −3°C | 0.9°C | 59 mm | 13 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00452030; 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 Dayton?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (5).
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 USC00452030.
When is the last frost in Dayton?
In Dayton, the last spring frost (32°F) comes after April 28 in half of years and after May 14 in one year in ten; the first autumn frost comes before October 13 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 281 year in 10 after May 14; 9 in 10 after April 11
- First autumn frost, half of years before
- October 131 year in 10 before September 30; 9 in 10 before October 29
NOAA puts the median frost-free season at 168 days, and the season without a hard freeze (28°F) at 203 days.
A hard freeze (28°F) comes after April 6 in half of springs and before October 25 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Dayton in zone 7a in ZIP code 99328, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Dayton's NOAA station is in zone 7b: the coldest night of a typical year reaches 6°F (21 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 USC00452030; 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 Dayton?
In a normal year in Dayton, 31 days a year reach 90°F (4 of them 100°F or more), 113 nights fall to 32°F or colder and 117 days bring measurable precipitation.
- Days at 90°F or more
- 31a normal year
- Days at 100°F or more
- 4a normal year
- Nights at 32°F or colder
- 113a normal year
- Days that stay below freezing
- 19high of 32°F or less
- Days with 0.01 inch of precipitation
- 117a normal year
- Days with 1 inch of snow or more
- 6a normal year
The highest temperature in this station's record (since 1893) is 114°F, on August 5, 1961; the lowest is −25°F, on December 30, 1968.
The wettest calendar year on that record is 1948, with 26.78 in; the snowiest season is 1949–50, with 44.6 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00452030; records: ACIS (NOAA Regional Climate Centers), station USC00452030. Records use complete months only; a month missing more than three days is left out.
How sunny is Dayton?
Over a year 81% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Dayton, 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 much heating and cooling does Dayton need?
A normal year in Dayton brings 5,622 heating degree days, 5% more than the median U.S. place (5,373), and 564 cooling degree days, 38% 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 2,541 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 963 | 0 |
| February | 778 | 0 |
| March | 668 | 0 |
| April | 468 | 1 |
| May | 262 | 20 |
| June | 120 | 70 |
| July | 21 | 215 |
| August | 29 | 198 |
| September | 143 | 59 |
| October | 453 | 2 |
| November | 746 | 0 |
| December | 973 | 0 |
| Year (annual) | 5,622 | 564 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00452030. 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.
Has Dayton been warmer than normal lately?
2024 averaged 51.7°F, 0.6°F above the 1991-2020 normal of 51.1°F. 3 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 52.5°F | +1.4°F | 14.99 | – |
| 2022 | 49.8°F | −1.3°F | 25.27 | – |
| 2023 | 51.6°F | +0.5°F | 14.03 | – |
| 2024 | 51.7°F | +0.6°F | 13.95 | 9.0 |
Over 94 complete years from 1905 to 2024, the station's annual mean temperature rose at a fitted 2.1°F per century (+0.12°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00452030; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Dayton's climate compare?
Dayton is warmer than 62 of the other 95 places with their own NOAA record in Washington, and wetter than 40. Across the 7,247 U.S. stations with normals, its annual mean of 51.1°F is warmer than 45%.
In the Köppen classification computed from these normals, Dayton is Csb: temperate, dry-summer, warm summer. 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 Dayton share this climate record?
2 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.
- Waitsburg, WA1,173 people · 8 mi SW
- Starbuck, WA138 people · 15 mi NW
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 Dayton's climate
What is the coldest month in Dayton?
December, with a normal high of 41°F and a normal low of 27°F. The warmest is July (88°F by day, 55°F at night).
Does it snow in Dayton?
Yes: 16 inches in a normal year, falling on 12 days with 0.1 inch or more, the most in January (6.3 inches).
What is the rainiest month in Dayton?
November, with 2.43 in of precipitation in a normal year; the driest is July with 0.39 in.
What plant hardiness zone is Dayton in?
The USDA's 2023 map puts Dayton in zone 7a in ZIP code 99328, the nearest ZIP area. By the same method at Dayton's NOAA station, the coldest night of a typical year reaches 6°F (21 years, 1991-2020): zone 7b.
How late can frost come in Dayton?
In half of years the last 32°F night comes after April 28; in one year in ten it comes after May 14. Waiting until May 14 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Washington climateThe statewide normals and every place in the state
- Walla Walla, WA21 miles from this station, 54.3°F a year
- Pomeroy, WA22 miles from this station, 49.8°F a year
- Whitman Mission, WA29 miles from this station, 51.7°F a year
- Milton-Freewater, OR32 miles from this station, 55.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made