Union, Oregon climate: Normal weather by month, frost dates and records
Union's normal year runs from 25°F December nights to 87°F August afternoons, with 14.8 inches of precipitation and 16 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.4°C, December lows of −4°C, August highs of 31°C, 375 mm of precipitation a year.
- NOAA stationUnion
- Station IDUSC00358746
- Location45.20°N 117.86°W
- Elevation2,777 ft (846 m)
- Population2,123
On October 22, the normal high in Union is 60°F and the normal low 33°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Union.
- Jan 40° 25°
- Feb 45° 27°
- Mar 53° 31°
- Apr 59° 34°
- May 68° 41°
- Jun 74° 47°
- Jul 86° 51°
- Aug 87° 50°
- Sep 77° 43°
- Oct 63° 34°
- Nov 48° 31°
- Dec 39° 25°
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 Union each month?
August is the warmest month, with normal highs of 87°F; December the coldest, with normal lows of 25°F. The most precipitation falls in May (2.47 in), the least in August (0.46 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 40°F | 25°F | 32.5°F | 1.19 | 5.3 | 13 | <1 | 24 | 9 h 10 min |
| February | 45°F | 27°F | 35.7°F | 0.93 | 2.9 | 10 | <1 | 20 | 10 h 20 min |
| March | 53°F | 31°F | 41.6°F | 1.26 | 1.2 | 11 | <1 | 19 | 11 h 50 min |
| April | 59°F | 34°F | 46.6°F | 1.68 | 0.4 | 13 | <1 | 12 | 13 h 30 min |
| May | 68°F | 41°F | 54.4°F | 2.47 | 0.1 | 13 | <1 | 3 | 14 h 50 min |
| June | 74°F | 47°F | 60.5°F | 1.69 | 0.0 | 10 | 2 | <1 | 15 h 40 min |
| July | 86°F | 51°F | 68.3°F | 0.48 | 0.0 | 4 | 12 | <1 | 15 h 20 min |
| August | 87°F | 50°F | 68.5°F | 0.46 | 0.0 | 4 | 12 | <1 | 14 h 10 min |
| September | 77°F | 43°F | 59.8°F | 0.70 | 0.0 | 5 | 3 | 2 | 12 h 40 min |
| October | 63°F | 34°F | 48.5°F | 1.15 | 0.0 | 9 | <1 | 13 | 11 h |
| November | 48°F | 31°F | 39.2°F | 1.53 | 1.4 | 13 | <1 | 17 | 9 h 30 min |
| December | 39°F | 25°F | 32.0°F | 1.22 | 4.9 | 12 | <1 | 25 | 8 h 50 min |
| Year (annual) | 61°F | 37°F | 49.0°F | 14.76 | 16.2 | 115 | 29 | 135 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 4°C | −4°C | 0.3°C | 30 mm | 13 cm |
| February | 7°C | −3°C | 2.1°C | 24 mm | 7 cm |
| March | 11°C | −1°C | 5.3°C | 32 mm | 3 cm |
| April | 15°C | 1°C | 8.1°C | 43 mm | 1 cm |
| May | 20°C | 5°C | 12.4°C | 63 mm | 0 cm |
| June | 24°C | 8°C | 15.8°C | 43 mm | 0 cm |
| July | 30°C | 11°C | 20.2°C | 12 mm | 0 cm |
| August | 31°C | 10°C | 20.3°C | 12 mm | 0 cm |
| September | 25°C | 6°C | 15.4°C | 18 mm | 0 cm |
| October | 17°C | 1°C | 9.2°C | 29 mm | 0 cm |
| November | 9°C | −1°C | 4.0°C | 39 mm | 4 cm |
| December | 4°C | −4°C | 0.0°C | 31 mm | 12 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00358746; 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 Union?
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 USC00358746.
When is the last frost in Union?
In Union, the last spring frost (32°F) comes after May 11 in half of years and after May 31 in one year in ten; the first autumn frost comes before September 26 in half of years and before September 9 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 111 year in 10 after May 31; 9 in 10 after April 26
- First autumn frost, half of years before
- September 261 year in 10 before September 9; 9 in 10 before October 10
NOAA puts the median frost-free season at 136 days, and the season without a hard freeze (28°F) at 166 days.
A hard freeze (28°F) comes after April 24 in half of springs and before October 7 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Union in zone 6b in ZIP code 97867, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Union's NOAA station is in zone 6b: the coldest night of a typical year reaches −1°F (17 complete years).
Frost dates for every NOAA station in Oregon · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00358746; 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 Union?
In a normal year in Union, 29 days a year reach 90°F (2 of them 100°F or more), 135 nights fall to 32°F or colder and 115 days bring measurable precipitation.
- Days at 90°F or more
- 29a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 135a normal year
- Days that stay below freezing
- 13high of 32°F or less
- Days with 0.01 inch of precipitation
- 115a normal year
- Days with 1 inch of snow or more
- 7a normal year
The highest temperature in this station's record (since 1911) is 108°F, on August 5, 1961; the lowest is −27°F, on January 18, 1943.
The wettest calendar year on that record is 1941, with 21.27 in; the snowiest season is 1955–56, with 68.7 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00358746; records: ACIS (NOAA Regional Climate Centers), station USC00358746. Records use complete months only; a month missing more than three days is left out.
How sunny is Union?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Union, 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 | 62% | 1.5 |
| February | 65% | 2.4 |
| March | 64% | 3.4 |
| April | 67% | 4.7 |
| May | 71% | 5.9 |
| June | 77% | 6.8 |
| July | 90% | 7.6 |
| August | 89% | 6.4 |
| September | 83% | 4.7 |
| October | 73% | 2.9 |
| November | 62% | 1.6 |
| December | 56% | 1.1 |
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 Union need?
A normal year in Union brings 6,190 heating degree days, 15% more than the median U.S. place (5,373), and 375 cooling degree days, 59% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,086 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,009 | 0 |
| February | 819 | 0 |
| March | 725 | 0 |
| April | 551 | 0 |
| May | 336 | 9 |
| June | 171 | 36 |
| July | 44 | 148 |
| August | 42 | 149 |
| September | 186 | 32 |
| October | 511 | 1 |
| November | 774 | 0 |
| December | 1,021 | 0 |
| Year (annual) | 6,190 | 375 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00358746. 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 Union's climate compare?
Union is warmer than 25 of the other 104 places with their own NOAA record in Oregon, and wetter than 27. Across the 7,247 U.S. stations with normals, its annual mean of 49.0°F is warmer than 36%.
In the Köppen classification computed from these normals, Union 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 Union 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.
- Cove, OR617 people · 7 mi N
- North Powder, OR498 people · 12 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 Union's climate
What is the coldest month in Union?
December, with a normal high of 39°F and a normal low of 25°F. The warmest is August (87°F by day, 50°F at night).
Does it snow in Union?
Yes: 16 inches in a normal year, falling on 17 days with 0.1 inch or more, the most in January (5.3 inches).
What is the rainiest month in Union?
May, with 2.47 in of precipitation in a normal year; the driest is August with 0.46 in.
What plant hardiness zone is Union in?
The USDA's 2023 map puts Union in zone 6b in ZIP code 97867, the nearest ZIP area. By the same method at Union's NOAA station, the coldest night of a typical year reaches −1°F (17 years, 1991-2020): zone 6b.
How late can frost come in Union?
In half of years the last 32°F night comes after May 11; in one year in ten it comes after May 31. Waiting until May 31 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Oregon climateThe statewide normals and every place in the state
- La Grande, OR13 miles from this station, 49.4°F a year
- Baker City, OR25 miles from this station, 47.6°F a year
- Elgin, OR25 miles from this station, 48.1°F a year
- Wallowa, OR30 miles from this station, 46.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made