Growing Degree Days in Montana
Montana has accumulated about 1147 GDD so far this year (base 50°F, since January 1), averaged across 5 NOAA USCRN stations. Station totals range from 665 to 1612 GDD. Through August 16, 2026. That is 65 GDD ahead of 2025, when Montana had banked 1082 GDD by August 16, based on 5 stations with records for both years.
How to Read This Number
Growing degree days count accumulated heat: each day adds the amount its average temperature runs above 50°F, the point where cool-season growth and most pests get going. Turf managers use the running total to time crabgrass pre-emergent, annual bluegrass seedhead suppression, plant growth regulator reapplication, and grub control. Treat it as a timing signal read against a model, not a fixed date. The total here is measured air temperature from NOAA USCRN stations, base 50°F, accumulated from January 1 — state the model whenever you compare totals, because a different base or start date is not interchangeable.
USCRN Stations in Montana (5)
| Station | GDD (base 50°F) | Through |
|---|---|---|
| Wolf Point 34 NE | 1,612 | Aug 16 |
| Wolf Point 29 ENE | 1,589 | Aug 16 |
| Dillon 18 WSW | 962 | Aug 15 |
| Lewistown 42 WSW | 907 | Aug 16 |
| St. Mary 1 SSW | 665 | Aug 16 |
Timing Windows for Montana
Where Montana sits against the published turf models. Each model carries its own base temperature and start date, so the accumulation column differs from row to row. A status of “varies by area” means the state’s coldest and warmest stations fall on opposite sides of the window.
| Model | Target | Montana now | Status |
|---|---|---|---|
| Crabgrass pre-emergent timerbase 32°F, from Feb 15 | 250 to 500 GDD | 2,793 to 3,874 | Passed |
| Crabgrass germination timerbase 50°F, from Feb 15 | 200 to 600 GDD | 665 to 1,612 | Passed |
| Spring broadleaf herbicide timerbase 50°F, from Feb 15 | 110 to 150 GDD, 150 to 200 GDD, 200 to 600 GDDby formulation | 665 to 1,612 | Passed |
| Japanese beetle adult emergencebase 50°F, from Jan 1 | 1030 to 2150 GDD | 665 to 1,612 | Varies by area |
| Poa annua seedhead suppression (Proxy/Primo)base 32°F, from Feb 15 | 200 to 500 GDD | 2,793 to 3,874 | Passed |
| Poa annua seedhead suppression (Embark)base 22°F, from Feb 15 | 680 to 1050 GDD | 4,412 to 5,489 | Passed |
| Poa annua seedhead flushbase 22°F, from Feb 15 | 1050 to 2900 GDD | 4,412 to 5,489 | Passed |
| Early-season dollar spot DMI applicationbase 50°F, from Feb 15 | 140 to 175 GDD | 665 to 1,612 | Passed |
| Growth regulator reapplication intervalbase 32°F, from Feb 15 | 200 GDD | 2,793 to 3,874 | Spacing, not a date |
| Broadleaf weed flowering timingsbase 50°F, from Feb 15 | Reference only | 665 to 1,612 | Reference |
| Legacy 50/86 modelbase 50°F / 86°F ceiling, from Feb 15 | Reference only | 1,012 to 1,843 | Reference |
Turf professional models are hidden by default. They cover putting greens and fairways rather than home lawns.
Michigan State ground-truthed these models in the Great Lakes region and does not recommend them for the mid-south transition zone or the South. Outside the Upper Midwest and Northeast, read them as a guide and confirm against local extension guidance.
How Montana Accumulated This Year
Most recent 14 reporting days
Daily and running totals, averaged across the state's 5 reporting stations. Days a station did not report are left out rather than counted as zero, so the dates can skip.
| Date | Daily | Total (base 50°F) | Total (base 32°F) |
|---|---|---|---|
| Aug 3 | 4.9 | 991 | 3,131 |
| Aug 4 | 5.1 | 996 | 3,154 |
| Aug 5 | 12.2 | 1,008 | 3,185 |
| Aug 6 | 14.3 | 1,023 | 3,217 |
| Aug 7 | 12.8 | 1,036 | 3,247 |
| Aug 8 | 15.8 | 1,051 | 3,281 |
| Aug 9 | 16.3 | 1,067 | 3,316 |
| Aug 10 | 13.9 | 1,082 | 3,348 |
| Aug 11 | 15.2 | 1,097 | 3,381 |
| Aug 12 | 12.3 | 1,109 | 3,411 |
| Aug 13 | 8.9 | 1,177 | 3,472 |
| Aug 14 | 10.3 | 1,242 | 3,579 |
| Aug 15 | 13.4 | 1,255 | 3,610 |
| Aug 16 | 14.8 | 1,193 | 3,558 |
Month by month, against last year
GDD earned in each month at base 50°F, this year beside 2025.
| Month | 2026 | 2025 | Base 32°F (2026) |
|---|---|---|---|
| January | 0 | 0 | 59 |
| February | 0 | 0 | 91 |
| March | 12 | 1 | 203 |
| April | 21 | 9 | 238 |
| May | 147 | 132 | 604 |
| June | 194 | 265 | 713 |
| July | 581 | 447 | 1,139 |
| August | 192 | 435 | 459 |
| September | — | 278 | — |
| October | — | 40 | — |
| November | — | 4 | — |
| December | — | 1 | — |
Cities in Montana (9)
Each city page pairs the current soil temperature from its nearest monitoring station with a local growing-degree-day total where a NOAA USCRN station is close enough to measure one.
Growing Degree Days FAQ for Montana
How many growing degree days has Montana accumulated this year?
Montana has accumulated about 1147 growing degree days (base 50°F, since January 1), averaged across 5 NOAA USCRN stations. Station totals range from 665 to 1612 GDD. The total climbs through summer and levels off as temperatures fall.
What base temperature and start date are these totals?
These are base 50°F growing degree days accumulated from January 1, the turf-industry convention. Each day adds the amount its average air temperature runs above 50°F, floored at zero. Totals from a different base or start date are not interchangeable, so the model is stated explicitly wherever a number appears.
What are growing degree days used for in lawn care?
Turf managers track the running total to time temperature-driven tasks: crabgrass pre-emergent before germination, annual bluegrass seedhead suppression, plant growth regulator reapplication, and grub control. Growing degree days are a timing signal read against a model, not a fixed calendar date.
How does Montana compare to last year?
Montana has banked 1147 GDD (base 50°F) through August 16. That is 65 GDD ahead of 2025, when Montana had banked 1082 GDD by August 16, based on 5 stations with records for both years.
Which growing degree day models does this page track for Montana?
This page reads Montana's accumulation against the published turf models, each on its own base temperature and start date: Michigan State's crabgrass pre-emergent timer (250 to 500 GDD base 32°F from February 15) and germination timer (200 to 600 GDD base 50°F), Purdue's spring broadleaf windows by formulation, Iowa State's Japanese beetle emergence range, and the professional models for annual bluegrass seedhead suppression, early-season dollar spot, and growth regulator intervals. A target range means nothing without its base and start date, so both travel with every number.
See growing degree days for every state, read the growing degree days lawn-care guide, or browse the full Montana soil temperature directory.