LawnWeather

Idaho Falls, ID Lawn Care Calendar

In a typical year, put down crabgrass preventer in Idaho Falls between May 3 and Jun 6. The best time to overseed is between Jul 20 and Sep 8. The last spring frost usually comes around May 11. Most lawns here are cool-season grass (tall fescue, Kentucky bluegrass, ryegrass).

Typical lawn care dates in Idaho Falls

Crabgrass preventer (pre-emergent)
May 3 – Jun 6
Spring fertilizer
May 30 – Jul 4
Overseeding & seeding
Jul 20 – Sep 8
Fall fertilizer
Aug 2 – Oct 21
Light band: typical frost-free season. Bars: typical windows.
TaskTypical window
Crabgrass preventer (pre-emergent)Crabgrass sprouts once soil stays above 55°F. Apply when soil reaches 50°F, before that happens.May 3 – Jun 6
Spring fertilizerA light feeding once soil warms past 55°F and the grass is actively growing.May 30 – Jul 4
Overseeding & seedingLate summer to early fall: seedlings need about 6–10 weeks of growth before the first frost.Jul 20 – Sep 8
Fall fertilizerThe most important feeding for cool-season grass, from early fall until soil cools to about 45°F.Aug 2 – Oct 21

Median dates, 2016–2025, from NOAA weather data for Idaho Falls. This year's dates can differ by a few weeks.

Month-by-month lawn care in Idaho Falls

  1. JanuaryNo treatments due; mow as needed.
  2. FebruaryNo treatments due; mow as needed.
  3. MarchNo treatments due; mow as needed.
  4. AprilNo treatments due; mow as needed.
  5. MayCrabgrass preventer (pre-emergent)Spring fertilizer
  6. JuneCrabgrass preventer (pre-emergent)Spring fertilizer
  7. JulySpring fertilizerOverseeding & seeding
  8. AugustOverseeding & seedingFall fertilizer
  9. SeptemberOverseeding & seedingFall fertilizer
  10. OctoberFall fertilizer
  11. NovemberNo treatments due; mow as needed.
  12. DecemberNo treatments due; mow as needed.

Soil temperature in Idaho Falls by month

Average soil temperature 4 inches down, estimated from 2016–2025 weather. It bottoms out in January at 20°F and peaks in July at 69°F. Crabgrass preventer goes down when it reaches 50°F, usually around May 3.

JanFebMarAprMayJunJulAugSepOctNovDec
20°F23°F34°F43°F52°F61°F69°F68°F60°F47°F35°F25°F

Idaho Falls lawn timing, year by year

Over the last 10 years, soil in Idaho Falls reached 50°F, the signal for crabgrass preventer, as early as Apr 10 (2016) and as late as May 16 (2022): 36 days apart. A fixed calendar date can't follow that, which is why the report above uses this year's soil temperature. Between the typical last spring frost (May 11) and first fall frost (Oct 3), the growing season lasts about 145 days.

YearCrabgrass window openedLast spring frostFirst fall frost
2025May 8Apr 23Oct 6
2024May 12May 3Oct 19
2023May 1Apr 29Oct 27
2022May 16May 24Oct 15
2021Apr 30May 11Sep 30
2020Apr 28May 9Sep 10
2019Apr 21Jun 10Sep 30
2018May 5May 3Sep 22
2017May 5May 19Sep 23
2016Apr 10May 12Oct 6

Estimated from daily temperatures for Idaho Falls. A dash means it didn't happen that year.

Frequently asked questions

When should I apply pre-emergent in Idaho Falls?

In a typical year, between May 3 and Jun 6. Put it down when soil reaches 50°F, before it stays above 55°F and crabgrass starts sprouting. Early springs move this up by a week or more, so check this year's soil temperature above.

When is the best time to plant grass seed in Idaho Falls?

Early fall, typically Jul 20 – Sep 8, while soil cools from 65°F toward 50°F.

When is the last frost in Idaho Falls?

The median last spring frost is May 11 and the median first fall frost is Oct 3 (2016–2025).

How long is the growing season in Idaho Falls?

About 145 days, from the median last spring frost on May 11 to the median first fall frost on Oct 3 (2016–2025).

Lawn care guides

More Idaho lawn calendars

Nearby cities in other states