Fall in zone 5bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 80403 (Coal Creek, CO)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, Ralston Rsvr, CO (4 miles away).
- Average last spring frostMay 350% chance of a 32°F freeze after this date
- Average first fall frostOct 1450% chance of a 32°F freeze by this date
- Growing season (frost-free)161 daysmedian, 32°F threshold
- USDA hardiness zone5b-15 to -10°F avg. coldest night
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This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Soil temperature now
2-inch depth
42°F Below 50°F
24-hour average · latest 41°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Boulder 14 W (19 mi).
4-inch depth
42°F Below 50°F
24-hour average · latest 42°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Boulder 14 W (19 mi).
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 80403 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 42°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent window is mostly past. Next: spring, when soil reaches 50°F (typically mid-April to mid-May).
Fertilizer window
Lawn region: Mountain West and High Plains. Timing only; always follow the product label.
- Kentucky bluegrass (cool-season): Early fall: Around Labor Day (late August–September); Late fall: Late October–November, before the ground freezes; Late spring: Optional around Memorial Day. Avoid: Early-spring and midsummer feeding (pushes top growth, favors crabgrass).
Plant now
No vegetable planting windows are open this week.
Prune now
No frost-timed pruning windows are open this week.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | Apr 21 |
| 50% (the "average" last frost) | May 3 |
| 10% (cautious: only 1 year in 10 freezes later) | May 17 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Sep 30 |
| 50% (the "average" first frost) | Oct 14 |
| 90% (late: most years have frozen by now) | Oct 28 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 12 | Oct 5 |
| 32°F (freeze) | May 3 | Oct 14 |
| 28°F (hard freeze) | Apr 25 | Oct 23 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 80403
Dates count from your average last spring frost (May 3) and first fall frost (Oct 14). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Mar 8–22 | May 10–24 (transplant) | – |
| Pepper (sweet and hot) | Feb 22–Mar 8 | May 17–31 (transplant) | – |
| Eggplant | Feb 22–Mar 8 | May 17–31 (transplant) | – |
| Tomatillo | Mar 8–22 | May 10–24 (transplant) | – |
| Lettuce | Mar 8–22 | Apr 12–May 3 (transplant) Apr 5–May 17 (sow outdoors) | Aug 19–Sep 9 (transplant) Aug 5–Sep 2 (sowing) |
| Spinach | – | Mar 22–Apr 12 (sow outdoors) | Aug 19–Sep 9 (sowing) |
| Kale | Mar 8–22 | Apr 5–19 (transplant) Apr 5–19 (sow outdoors) | Jul 22–Aug 19 (transplant) Jul 8–Aug 5 (sowing) |
| Collards | Mar 8–22 | Apr 5–May 3 (transplant) Apr 5–May 3 (sow outdoors) | Jul 22–Aug 19 (transplant) Jul 8–Aug 5 (sowing) |
| Broccoli | Feb 22–Mar 8 | Apr 5–19 (transplant) | Jul 8–Aug 5 (transplant) |
| Cabbage | Feb 22–Mar 8 | Apr 5–19 (transplant) | Jul 8–Aug 5 (transplant) |
| Cauliflower | Feb 22–Mar 8 | Apr 19–May 3 (transplant) | Jul 8–Aug 5 (transplant) |
| Brussels sprouts | Feb 8–22 | Apr 5–19 (transplant) | Jun 24–Jul 15 (transplant) |
| Kohlrabi | Mar 8–22 | Apr 5–19 (transplant) Apr 5–19 (sow outdoors) | Aug 5–19 (sowing) |
| Bok choy / Asian greens | – | Apr 5–19 (sow outdoors) | Aug 19–Sep 2 (sowing) |
| Arugula | – | Apr 5–May 3 (sow outdoors) | Aug 19–Sep 16 (sowing) |
| Mustard greens | – | Apr 5–26 (sow outdoors) | Aug 19–Sep 2 (sowing) |
| Swiss chard | Mar 22–Apr 5 | Apr 19–May 10 (transplant) Apr 19–May 17 (sow outdoors) | Aug 5–19 (sowing) |
| Beet | – | Apr 5–May 3 (sow outdoors) | Aug 5–19 (sowing) |
| Carrot | – | Apr 12–May 10 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Radish | – | Mar 29–May 10 (sow outdoors) | Sep 2–16 (sowing) |
| Turnip | – | Apr 5–26 (sow outdoors) | Aug 5–19 (sowing) |
| Parsnip | – | Apr 12–May 3 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 8–Apr 5 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Onion (bulbing) | Feb 8–22 | Mar 22–Apr 5 (transplant) | – |
| Green onion / scallion | – | Mar 22–Apr 19 (sow outdoors) | Aug 5–19 (sowing) |
| Leek | Feb 8–22 | Apr 5–19 (transplant) | – |
| Garlic | – | – | Sep 2–30 (sowing) |
| Shallot | – | Mar 22–Apr 5 (transplant) | Sep 2–30 (sowing) |
| Potato | – | Apr 5–19 (transplant) | Jun 24–Jul 8 (transplant) |
| Sweet potato | – | May 24–Jun 7 (transplant) | – |
| Sweet corn | – | May 10–24 (sow outdoors) | – |
| Bean, bush (snap) | – | May 10–24 (sow outdoors) | – |
| Bean, pole | – | May 10–24 (sow outdoors) | – |
| Lima bean | – | May 17–31 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 24–Jun 14 (sow outdoors) | – |
| Cucumber | Apr 5–12 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Summer squash / zucchini | Apr 5–12 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Winter squash | Apr 5–12 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Pumpkin | – | May 10–24 (sow outdoors) | – |
| Watermelon | Apr 5–12 | May 17–31 (transplant) May 17–31 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 5–12 | May 17–31 (transplant) May 17–31 (sow outdoors) | – |
| Okra | Mar 22–Apr 5 | May 17–31 (transplant) May 17–31 (sow outdoors) | – |
| Celery | Feb 8–22 | May 10–17 (transplant) | – |
| Basil | Mar 22–Apr 5 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Cilantro | – | Apr 19–May 17 (sow outdoors) | Aug 19–Sep 2 (sowing) |
| Parsley | Feb 22–Mar 8 | Apr 19–May 3 (transplant) Apr 12–May 3 (sow outdoors) | – |
| Dill | – | May 3–17 (sow outdoors) | Aug 19–Sep 2 (sowing) |
| Sunflower | – | May 3–17 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 5–19 (transplant) | – |
| Rhubarb (crowns) | – | Apr 5–19 (transplant) | – |
| Strawberry (plants) | – | Apr 5–19 (transplant) | Aug 5–Sep 2 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Plants that do well here
Colorado has a university or garden plant program: Plant Select®. Plant frost-tender annuals after May 3 here (the average last frost). Not affiliated with the program.
Where these numbers come from
Station: Ralston Rsvr, CO (NOAA GHCN-Daily ID USC00056816), elevation 5,900 ft, 4.3 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Coal Creek Canyon, CO | 6 mi | Jun 5 | Sep 16 |
| Gross Rsvr, CO | 8 mi | May 24 | Sep 23 |
| Wheat Ridge 2, CO | 11 mi | May 5 | Oct 5 |
The average last-frost dates of these stations span 33 days, a rough guide to local variation. See data sources & methods.
Frost questions for 80403
When is the last frost in 80403?
The average (50% chance) last spring freeze of 32°F for ZIP 80403 is May 3. For a more cautious planting date, use May 17, when only 1 year in 10 still sees a later freeze.
When is the first frost in 80403?
The average first fall freeze is October 14. In 1 year in 10 it comes by September 30.
What hardiness zone is 80403?
ZIP 80403 is in USDA zone 5b (-15 to -10°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 80403 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
80025 Eldorado Springs 80007 Arvada 80401 Golden 80471 80419 Golden 80005 Arvada 80004 Arvada 80305 Boulder
Other ZIP codes in Jefferson County
80002 80003 80004 80005 80007 80021 80033 80123 80127 80128 80214 80215 80226 80227 80228 80232 80235 80401 80419 80425 80433 80453 80454 80457 All Jefferson County frost dates · Colorado frost dates
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Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
- Freeze alerts
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Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.