Boulder, Colorado · Nov 11, 2026
Soil temperature today in Boulder
low 46°F · high 54°F
Modelled by NOAA GFS · run Nov 11, 12:00 UTC (7 am Eastern) · grid cell 2.4 km from Boulder
What the soil says today
- Pre-emergentSeason over
- Cool-season seedToo late in the season
- Warm-season seedToo cold
- TomatoesToo cold
- Peas and lettuceWarm enough
From the 5-day mean of the modelled 0–4 in layer.
Soil temperature, 0–4 in: last 7 days and next 7
°F. Dots and line: daily average (dashed = forecast); bars: the day's low to high; green band: the 50–55°F pre-emergent window.
- Daily average
- Low to high
- 50–55°F window
View as table
| Day | Average | Low | High | |
|---|---|---|---|---|
| Nov 4 | 45.2°F | 41.5°F | 49.5°F | analysis |
| Nov 5 | 45.9°F | 41.7°F | 50.9°F | analysis |
| Nov 6 | 45.5°F | 41.7°F | 50.2°F | analysis |
| Nov 7 | 46.6°F | 42.2°F | 52.1°F | analysis |
| Nov 8 | 48.4°F | 44.2°F | 53.4°F | analysis |
| Nov 9 | 50.4°F | 46.3°F | 56.0°F | analysis |
| Nov 10 | 50.2°F | 45.6°F | 55.0°F | analysis |
| Today | 50.0°F | 46.5°F | 53.5°F | forecast |
| Nov 12 | 49.6°F | 45.4°F | 54.6°F | forecast |
| Nov 13 | 49.0°F | 46.0°F | 52.1°F | forecast |
| Nov 14 | 46.2°F | 42.9°F | 49.2°F | forecast |
| Nov 15 | 45.2°F | 41.4°F | 49.3°F | forecast |
| Nov 16 | 44.1°F | 40.0°F | 48.5°F | forecast |
| Nov 17 | 44.5°F | 40.2°F | 49.8°F | forecast |
What the soil says for each job
Today's verdicts use the 5-day mean of the modelled 0–4 in layer.
| Job | Soil rule | Today |
|---|---|---|
| Crabgrass pre-emergent | Apply while the soil holds 50 to 55°F, before crabgrass germinates at about 55°F | Season over The spring window is closed. It opens again when the soil holds 50°F. Last spring the soil held 50°F from Mar 20 and 55°F from Mar 21. |
| Seed or overseed cool-season grass | Fescue, bluegrass and ryegrass germinate best in soil of 50 to 65°F | Too late in the season Past the usual Aug 15 to Oct 15 seeding window (49°F soil today). |
| Seed warm-season grass | Bermuda, zoysia and centipede need soil of 65°F or more | Too cold 49°F: under 65°F. |
| Plant out tomatoes | Tomato roots want soil of 60°F or more (check your frost date as well) | Too cold 49°F: under 60°F. |
| Sow peas, lettuce and spinach | Cool-weather crops germinate once soil reaches about 40°F | Warm enough 49°F: at or over 40°F. |
The 2026 season so far
°F, daily average of the 0–4 in layer since 1 January (dashed = forecast). Dots: the days the soil began to hold 50°F and 55°F.
- Daily average
- 50–55°F window
When the soil crossed each threshold
2026, from the 5-day mean held for 10 days or more.
| Soil | What it means | Held from (spring 2026) | Fell below (autumn 2026) |
|---|---|---|---|
| 40°F | Peas and lettuce can be sown | Feb 6 | not yet |
| 50°F | Pre-emergent window opens | Mar 20 | not yet |
| 55°F | Crabgrass can germinate | Mar 21 | Oct 27 |
| 60°F | Warm enough for tomatoes | May 27 | Oct 15 |
| 65°F | Warm-season grass seed | Jun 6 | Sep 21 |
Growing degree days in Boulder
Base 50°F, from 1 January to Nov 8, at the Boulder Muni Airport station (5 km).
A growing degree day is each degree that the day's average temperature runs above 50°F. Insects, weeds and crops develop by accumulated GDD, so the number says how far the season has run. Every city.
Soil temperature nearby
Each from a different model grid cell.
| City | Distance | Soil today | vs a week ago | Grass seed |
|---|---|---|---|---|
| Brighton, CO | 38 km | 51°F | +2°F | Too late in the season |
| Denver, CO | 39 km | 57°F | +3°F | Too late in the season |
| Fort Collins, CO | 65 km | 52°F | +1°F | Too late in the season |
| Greeley, CO | 66 km | 52°F | +3°F | Too late in the season |
| Castle Rock, CO | 80 km | 47°F | +2°F | Too late in the season |
| Cheyenne, WY | 131 km | 49°F | +6°F | Too late in the season |
This page also covers Longmont (22.2 km), Broomfield (18.9 km), Lafayette (15.6 km), Erie (19.2 km), Louisville (12.5 km): they share the same model grid cell area, within 25 km.
Questions
- What is the soil temperature in Boulder today?
- About 50°F on average in the top 4 inches (0–10 cm), with a low of 46°F and a high of 54°F, from NOAA's GFS model run of Nov 11, 12:00 UTC (7 am Eastern).
- Is it time to put down crabgrass preventer in Boulder?
- The spring window is closed. It opens again when the soil holds 50°F. Last spring the soil held 50°F from Mar 20 and 55°F from Mar 21.
- When did the soil in Boulder reach 55°F this year?
- The 5-day average held 55°F from Mar 21, 2026.
- How accurate is a modelled soil temperature?
- Against NOAA's 108 reference stations the model's daily average was off by 4.2°F on average, and within 5°F on 68% of days. A shaded, mulched or watered yard can differ more.
Data: Global Forecast System (GFS) 0.25°, soil temperature 0–10 cm (TSOIL) (NOAA National Centers for Environmental Prediction (NCEP)); U.S. Climate Reference Network (USCRN) hourly data, version 2 (soil temperature at 5 cm and 10 cm, air temperature) (NOAA National Centers for Environmental Information (NCEI)); Global Historical Climatology Network - Daily (GHCN-Daily), daily maximum and minimum temperature (NOAA National Centers for Environmental Information (NCEI)); GeoNames gazetteer (cities15000) (GeoNames).