Bynum, Montana climate: Normal weather by month, frost dates and records
Bynum's normal year runs from 14°F January nights to 80°F July afternoons, with 15.3 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.4°C, January lows of −10°C, July highs of 27°C, 390 mm of precipitation a year.
- NOAA stationBynum (4 mi SSE)
- Station IDUSC00241342
- Location47.93°N 112.29°W
- Elevation4,039 ft (1,231 m)
- From the center3 miles
- Population (census place)12
On October 8, the normal high in Bynum is 59°F and the normal low 35°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Bynum.
- Jan 36° 14°
- Feb 36° 15°
- Mar 44° 21°
- Apr 51° 29°
- May 62° 39°
- Jun 71° 47°
- Jul 80° 52°
- Aug 79° 51°
- Sep 70° 43°
- Oct 55° 32°
- Nov 43° 23°
- Dec 35° 16°
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 Bynum each month?
July is the warmest month, with normal highs of 80°F; January the coldest, with normal lows of 14°F. The most precipitation falls in May (2.64 in), the least in February (0.43 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 36°F | 14°F | 25.2°F | 0.60 | – | <1 | 27 | 8 h 50 min |
| February | 36°F | 15°F | 25.5°F | 0.43 | – | <1 | 26 | 10 h 10 min |
| March | 44°F | 21°F | 32.2°F | 1.06 | – | <1 | 27 | 11 h 50 min |
| April | 51°F | 29°F | 40.3°F | 2.11 | – | <1 | 18 | 13 h 40 min |
| May | 62°F | 39°F | 50.2°F | 2.64 | – | <1 | 4 | 15 h 10 min |
| June | 71°F | 47°F | 58.5°F | 2.49 | – | 1 | <1 | 16 h |
| July | 80°F | 52°F | 66.2°F | 1.55 | – | 4 | <1 | 15 h 40 min |
| August | 79°F | 51°F | 65.4°F | 1.32 | – | 3 | <1 | 14 h 20 min |
| September | 70°F | 43°F | 56.4°F | 1.19 | – | <1 | 2 | 12 h 40 min |
| October | 55°F | 32°F | 43.5°F | 1.02 | – | <1 | 15 | 11 h |
| November | 43°F | 23°F | 33.1°F | 0.49 | – | <1 | 23 | 9 h 20 min |
| December | 35°F | 16°F | 25.4°F | 0.44 | – | <1 | 28 | 8 h 20 min |
| Year (annual) | 55°F | 32°F | 43.5°F | 15.34 | – | 9 | 169 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 2°C | −10°C | −3.8°C | 15 mm |
| February | 2°C | −9°C | −3.6°C | 11 mm |
| March | 6°C | −6°C | 0.1°C | 27 mm |
| April | 11°C | −2°C | 4.6°C | 54 mm |
| May | 16°C | 4°C | 10.1°C | 67 mm |
| June | 21°C | 8°C | 14.7°C | 63 mm |
| July | 27°C | 11°C | 19.0°C | 39 mm |
| August | 26°C | 11°C | 18.6°C | 34 mm |
| September | 21°C | 6°C | 13.6°C | 30 mm |
| October | 13°C | 0°C | 6.4°C | 26 mm |
| November | 6°C | −5°C | 0.6°C | 12 mm |
| December | 1°C | −9°C | −3.7°C | 11 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Choteau (9 miles away), gets 48 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00241342; 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 Bynum?
Normal highs sit between 65°F and 85°F in June, July, August 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 USC00241342.
When is the last frost in Bynum?
In Bynum, the last spring frost (32°F) comes after May 16 in half of years and after May 28 in one year in ten; the first autumn frost comes before September 27 in half of years and before September 16 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 161 year in 10 after May 28; 9 in 10 after May 2
- First autumn frost, half of years before
- September 271 year in 10 before September 16; 9 in 10 before October 9
NOAA puts the median frost-free season at 133 days, and the season without a hard freeze (28°F) at 157 days.
A hard freeze (28°F) comes after May 2 in half of springs and before October 6 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Bynum in zone 4b in ZIP code 59419, the nearest ZIP area.
Frost dates for every NOAA station in Montana · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00241342; 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 Bynum?
In a normal year in Bynum, 9 days a year reach 90°F and 169 nights fall to 32°F or colder.
- Days at 90°F or more
- 9a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 169a normal year
- Days that stay below freezing
- 45high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00241342.
How sunny is Bynum?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Bynum, 3.9 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (60%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 64% | 1.4 |
| February | 69% | 2.4 |
| March | 66% | 3.5 |
| April | 66% | 4.6 |
| May | 67% | 5.6 |
| June | 73% | 6.4 |
| July | 87% | 7.3 |
| August | 83% | 5.9 |
| September | 77% | 4.3 |
| October | 69% | 2.6 |
| November | 61% | 1.5 |
| December | 60% | 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 Bynum need?
A normal year in Bynum brings 8,040 heating degree days, 50% more than the median U.S. place (5,373), and 221 cooling degree days, 76% 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 1,679 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,236 | 0 |
| February | 1,106 | 0 |
| March | 1,018 | 0 |
| April | 742 | 0 |
| May | 460 | 2 |
| June | 209 | 14 |
| July | 59 | 96 |
| August | 78 | 89 |
| September | 278 | 19 |
| October | 668 | 2 |
| November | 959 | 0 |
| December | 1,227 | 0 |
| Year (annual) | 8,040 | 221 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00241342. 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 Bynum been warmer than normal lately?
2023 averaged 44.9°F, 1.4°F above the 1991-2020 normal of 43.5°F. 2 of the 2 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 43.6°F | +0.1°F | 9.81 |
| 2023 | 44.9°F | +1.4°F | 13.28 |
Source: observed years: ACIS, station USC00241342. A year counts only with all twelve months complete.
How does Bynum's climate compare?
Bynum is warmer than 56 of the other 140 places with their own NOAA record in Montana, and wetter than 81. Across the 7,247 U.S. stations with normals, its annual mean of 43.5°F is warmer than 14%.
In the Köppen classification computed from these normals, Bynum 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 Bynum share this climate record?
Miller Colony 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.
- Miller Colony, MT0 people · 0 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 Bynum's climate
What is the coldest month in Bynum?
January, with a normal high of 36°F and a normal low of 14°F. The warmest is July (80°F by day, 52°F at night).
Does it snow in Bynum?
Yes. NOAA publishes no 1991-2020 snowfall normal for Bynum's NOAA station; the nearest record that keeps one, Choteau (9 miles away), records 48 inches of snow in a normal year.
What is the rainiest month in Bynum?
May, with 2.64 in of precipitation in a normal year; the driest is February with 0.43 in.
What plant hardiness zone is Bynum in?
The USDA's 2023 map puts Bynum in zone 4b in ZIP code 59419, the nearest ZIP area.
How late can frost come in Bynum?
In half of years the last 32°F night comes after May 16; in one year in ten it comes after May 28. Waiting until May 28 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Choteau, MT9 miles from this station, 43.8°F a year
- Blackleaf, MT9 miles from this station, 41.3°F a year
- Conrad, MT23 miles from this station, 43.7°F a year
- Fairfield, MT25 miles from this station, 44.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made