Hartline, Washington climate: Normal weather by month, frost dates and records
Hartline's normal year runs from 23°F January nights to 86°F July afternoons, with 10.9 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.3°C, January lows of −5°C, July highs of 30°C, 277 mm of precipitation a year.
- NOAA stationHartline
- Station IDUSC00453529
- Location47.69°N 119.11°W
- Elevation1,906 ft (581 m)
- Population177
On October 23, the normal high in Hartline is 56°F and the normal low 35°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Hartline.
- Jan 32° 23°
- Feb 40° 25°
- Mar 50° 31°
- Apr 60° 36°
- May 70° 44°
- Jun 76° 49°
- Jul 86° 57°
- Aug 86° 57°
- Sep 76° 48°
- Oct 60° 38°
- Nov 43° 29°
- Dec 33° 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 in Hartline each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 23°F. The most precipitation falls in December (1.57 in), the least in September (0.34 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 32°F | 23°F | 27.5°F | 1.34 | – | <1 | 29 | 8 h 50 min |
| February | 40°F | 25°F | 32.6°F | 0.72 | – | <1 | 23 | 10 h 10 min |
| March | 50°F | 31°F | 40.2°F | 1.04 | – | <1 | 19 | 11 h 50 min |
| April | 60°F | 36°F | 47.6°F | 0.81 | – | <1 | 9 | 13 h 30 min |
| May | 70°F | 44°F | 56.6°F | 1.09 | – | 1 | 2 | 15 h 10 min |
| June | 76°F | 49°F | 62.8°F | 0.89 | – | 3 | <1 | 16 h |
| July | 86°F | 57°F | 71.6°F | 0.55 | – | 14 | <1 | 15 h 40 min |
| August | 86°F | 57°F | 71.2°F | 0.38 | – | 12 | <1 | 14 h 20 min |
| September | 76°F | 48°F | 62.2°F | 0.34 | – | 3 | <1 | 12 h 40 min |
| October | 60°F | 38°F | 49.0°F | 0.91 | – | <1 | 7 | 11 h |
| November | 43°F | 29°F | 36.4°F | 1.25 | – | <1 | 20 | 9 h 20 min |
| December | 33°F | 23°F | 27.6°F | 1.57 | – | <1 | 27 | 8 h 30 min |
| Year (annual) | 59°F | 38°F | 48.8°F | 10.89 | – | 32 | 136 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 0°C | −5°C | −2.5°C | 34 mm |
| February | 4°C | −4°C | 0.3°C | 18 mm |
| March | 10°C | −1°C | 4.6°C | 26 mm |
| April | 15°C | 2°C | 8.7°C | 21 mm |
| May | 21°C | 7°C | 13.7°C | 28 mm |
| June | 25°C | 10°C | 17.1°C | 23 mm |
| July | 30°C | 14°C | 22.0°C | 14 mm |
| August | 30°C | 14°C | 21.8°C | 10 mm |
| September | 25°C | 9°C | 16.8°C | 9 mm |
| October | 16°C | 3°C | 9.4°C | 23 mm |
| November | 6°C | −1°C | 2.4°C | 32 mm |
| December | 0°C | −5°C | −2.4°C | 40 mm |
NOAA publishes no 1991-2020 snowfall normal for this station, and no record within 25 miles keeps one, so snow is left out here rather than estimated.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00453529; 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 Hartline?
Normal highs sit between 65°F and 85°F in May, June and September.
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 USC00453529.
When is the last frost in Hartline?
In Hartline, the last spring frost (32°F) comes after May 2 in half of years and after May 22 in one year in ten; the first autumn frost comes before October 12 in half of years and before September 27 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 21 year in 10 after May 22; 9 in 10 after April 17
- First autumn frost, half of years before
- October 121 year in 10 before September 27; 9 in 10 before October 29
NOAA puts the median frost-free season at 162 days, and the season without a hard freeze (28°F) at 192 days.
A hard freeze (28°F) comes after April 16 in half of springs and before October 25 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Hartline in zone 6b in ZIP code 99135, the nearest ZIP area.
Frost dates for every NOAA station in Washington · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00453529; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Hartline?
In a normal year in Hartline, 32 days a year reach 90°F (3 of them 100°F or more) and 136 nights fall to 32°F or colder.
- Days at 90°F or more
- 32a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 136a normal year
- Days that stay below freezing
- 30high of 32°F or less
The highest temperature in this station's record (since 1929) is 110°F, on July 19, 1960; the lowest is −20°F, on February 8, 1933.
The wettest calendar year on that record is 1948, with 20.16 in; the snowiest season is 1948–49, with 57.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00453529; records: ACIS (NOAA Regional Climate Centers), station USC00453529. Records use complete months only; a month missing more than three days is left out.
How sunny is Hartline?
Over a year 80% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Hartline, 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 much heating and cooling does Hartline need?
A normal year in Hartline brings 6,443 heating degree days, 20% more than the median U.S. place (5,373), and 560 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 2,437 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,162 | 0 |
| February | 907 | 0 |
| March | 769 | 0 |
| April | 522 | 0 |
| May | 273 | 13 |
| June | 121 | 56 |
| July | 18 | 223 |
| August | 17 | 211 |
| September | 142 | 56 |
| October | 496 | 1 |
| November | 858 | 0 |
| December | 1,158 | 0 |
| Year (annual) | 6,443 | 560 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00453529. 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 Hartline been warmer than normal lately?
Over 38 complete years from 1936 to 2019, the station's annual mean temperature rose at a fitted -1.6°F per century (−0.09°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 Hartline's climate compare?
Hartline is warmer than 22 of the other 95 places with their own NOAA record in Washington, and wetter than 16. Across the 7,247 U.S. stations with normals, its annual mean of 48.8°F is warmer than 35%.
In the Köppen classification computed from these normals, Hartline 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 Hartline 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.
- Coulee City, WA554 people · 10 mi SW
- Almira, WA328 people · 8 mi E
- Banks Lake South, WA216 people · 9 mi SW
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 Hartline's climate
What is the coldest month in Hartline?
January, with a normal high of 32°F and a normal low of 23°F. The warmest is July (86°F by day, 57°F at night).
What is the rainiest month in Hartline?
December, with 1.57 in of precipitation in a normal year; the driest is September with 0.34 in.
What plant hardiness zone is Hartline in?
The USDA's 2023 map puts Hartline in zone 6b in ZIP code 99135, the nearest ZIP area.
How late can frost come in Hartline?
In half of years the last 32°F night comes after May 2; in one year in ten it comes after May 22. Waiting until May 22 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Washington climateThe statewide normals and every place in the state
- Wilbur, WA19 miles from this station, 45.6°F a year
- Coulee Dam, WA19 miles from this station, 49.9°F a year
- Odessa, WA31 miles from this station, 48.8°F a year
- Ephrata, WA32 miles from this station, 51.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made