Fall in zone 8bPhoto: George Chernilevsky, Public domain, via Wikimedia Commons
Frost dates for ZIP 98603 (Cowlitz County, WA)
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, Cougar 6 E, WA (10 miles away).
- Average last spring frostApr 150% chance of a 32°F freeze after this date
- Average first fall frostNov 1850% chance of a 32°F freeze by this date
- Growing season (frost-free)227 daysmedian, 32°F threshold
- USDA hardiness zone8b15 to 20°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
No soil station with a fresh reading within 62 miles.
4-inch depth
No soil station with a fresh reading within 62 miles.
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 98603 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
No soil reading near this ZIP. Typical extension timing for your region: spring March to April.
Fertilizer window
Lawn region: Pacific Northwest (west of the Cascades). Timing only; always follow the product label.
- Perennial ryegrass (cool-season): Early fall: September; Late fall: October–November; Overseeded Bermuda: Light feeding once the winter rye is established, if needed. Avoid: Summer feeding.
Plant now
- Arugula: fall sowing Sep 23–Oct 21
- Radish: fall sowing Oct 7–21
- Garlic: fall sowing Oct 7–Nov 4
- Shallot: fall sowing Oct 7–Nov 4
Prune now
No frost-timed pruning windows are open this week.
Your average first frost is Nov 18: skip heavy pruning in the 6–8 weeks before it, because new growth may not harden off in time.
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) | Mar 6 |
| 50% (the "average" last frost) | Apr 1 |
| 10% (cautious: only 1 year in 10 freezes later) | May 2 |
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) | Oct 29 |
| 50% (the "average" first frost) | Nov 18 |
| 90% (late: most years have frozen by now) | Dec 8 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 2 | Oct 29 |
| 32°F (freeze) | Apr 1 | Nov 18 |
| 28°F (hard freeze) | Feb 22 | Dec 7 |
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 98603
Dates count from your average last spring frost (Apr 1) and first fall frost (Nov 18). 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 | Feb 4–18 | Apr 8–22 (transplant) | Jul 22–Aug 19 (transplant) |
| Pepper (sweet and hot) | Jan 21–Feb 4 | Apr 15–29 (transplant) | Jul 29–Aug 19 (transplant) |
| Eggplant | Jan 21–Feb 4 | Apr 15–29 (transplant) | Jul 29–Aug 19 (transplant) |
| Tomatillo | Feb 4–18 | Apr 8–22 (transplant) | – |
| Lettuce | Feb 4–18 | Mar 11–Apr 1 (transplant) Mar 4–Apr 15 (sow outdoors) | Sep 23–Oct 14 (transplant) Sep 9–Oct 7 (sowing) |
| Spinach | – | Feb 18–Mar 11 (sow outdoors) | Sep 23–Oct 14 (sowing) |
| Kale | Feb 4–18 | Mar 4–18 (transplant) Mar 4–18 (sow outdoors) | Aug 26–Sep 23 (transplant) Aug 12–Sep 9 (sowing) |
| Collards | Feb 4–18 | Mar 4–Apr 1 (transplant) Mar 4–Apr 1 (sow outdoors) | Aug 26–Sep 23 (transplant) Aug 12–Sep 9 (sowing) |
| Broccoli | Jan 21–Feb 4 | Mar 4–18 (transplant) | Aug 12–Sep 9 (transplant) |
| Cabbage | Jan 21–Feb 4 | Mar 4–18 (transplant) | Aug 12–Sep 9 (transplant) |
| Cauliflower | Jan 21–Feb 4 | Mar 18–Apr 1 (transplant) | Aug 12–Sep 9 (transplant) |
| Brussels sprouts | Jan 7–21 | Mar 4–18 (transplant) | Jul 29–Aug 19 (transplant) |
| Kohlrabi | Feb 4–18 | Mar 4–18 (transplant) Mar 4–18 (sow outdoors) | Sep 9–23 (sowing) |
| Bok choy / Asian greens | – | Mar 4–18 (sow outdoors) | Sep 23–Oct 7 (sowing) |
| Arugula | – | Mar 4–Apr 1 (sow outdoors) | Sep 23–Oct 21 (sowing) |
| Mustard greens | – | Mar 4–25 (sow outdoors) | Sep 23–Oct 7 (sowing) |
| Swiss chard | Feb 18–Mar 4 | Mar 18–Apr 8 (transplant) Mar 18–Apr 15 (sow outdoors) | Sep 9–23 (sowing) |
| Beet | – | Mar 4–Apr 1 (sow outdoors) | Sep 9–23 (sowing) |
| Carrot | – | Mar 11–Apr 8 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Radish | – | Feb 25–Apr 8 (sow outdoors) | Oct 7–21 (sowing) |
| Turnip | – | Mar 4–25 (sow outdoors) | Sep 9–23 (sowing) |
| Parsnip | – | Mar 11–Apr 1 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Feb 4–Mar 4 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Onion (bulbing) | Jan 7–21 | Feb 18–Mar 4 (transplant) | – |
| Green onion / scallion | – | Feb 18–Mar 18 (sow outdoors) | Sep 9–23 (sowing) |
| Leek | Jan 7–21 | Mar 4–18 (transplant) | – |
| Garlic | – | – | Oct 7–Nov 4 (sowing) |
| Shallot | – | Feb 18–Mar 4 (transplant) | Oct 7–Nov 4 (sowing) |
| Potato | – | Mar 4–18 (transplant) | Jul 29–Aug 12 (transplant) |
| Sweet potato | – | Apr 22–May 6 (transplant) | – |
| Sweet corn | – | Apr 8–22 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 8–22 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Bean, pole | – | Apr 8–22 (sow outdoors) | – |
| Lima bean | – | Apr 15–29 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Apr 22–May 13 (sow outdoors) | – |
| Cucumber | Mar 4–11 | Apr 8–22 (transplant) Apr 8–22 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Summer squash / zucchini | Mar 4–11 | Apr 8–22 (transplant) Apr 8–22 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Winter squash | Mar 4–11 | Apr 8–22 (transplant) Apr 8–22 (sow outdoors) | – |
| Pumpkin | – | Apr 8–22 (sow outdoors) | – |
| Watermelon | Mar 4–11 | Apr 15–29 (transplant) Apr 15–29 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 4–11 | Apr 15–29 (transplant) Apr 15–29 (sow outdoors) | – |
| Okra | Feb 18–Mar 4 | Apr 15–29 (transplant) Apr 15–29 (sow outdoors) | – |
| Celery | Jan 7–21 | Apr 8–15 (transplant) | – |
| Basil | Feb 18–Mar 4 | Apr 8–22 (transplant) Apr 8–22 (sow outdoors) | – |
| Cilantro | – | Mar 18–Apr 15 (sow outdoors) | Sep 23–Oct 7 (sowing) |
| Parsley | Jan 21–Feb 4 | Mar 18–Apr 1 (transplant) Mar 11–Apr 1 (sow outdoors) | – |
| Dill | – | Apr 1–15 (sow outdoors) | Sep 23–Oct 7 (sowing) |
| Sunflower | – | Apr 1–15 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 4–18 (transplant) | – |
| Rhubarb (crowns) | – | Mar 4–18 (transplant) | – |
| Strawberry (plants) | – | Mar 4–18 (transplant) | Sep 9–Oct 7 (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.
Where these numbers come from
Station: Cougar 6 E, WA (NOAA GHCN-Daily ID USC00451760), elevation 659 ft, 10.1 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Battle Ground, WA | 20 mi | Apr 26 | Oct 16 |
| Carson Fish Hatchery, WA | 25 mi | May 2 | Oct 9 |
| Longview, WA | 25 mi | Apr 8 | Nov 5 |
The average last-frost dates of these stations span 32 days, a rough guide to local variation. See data sources & methods.
Frost questions for 98603
When is the last frost in 98603?
The average (50% chance) last spring freeze of 32°F for ZIP 98603 is April 1. For a more cautious planting date, use May 2, when only 1 year in 10 still sees a later freeze.
When is the first frost in 98603?
The average first fall freeze is November 18. In 1 year in 10 it comes by October 29.
What hardiness zone is 98603?
ZIP 98603 is in USDA zone 8b (15 to 20°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 98603 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
98601 Amboy 98625 Kalama 98616 Cougar 98675 Yacolt 98674 Woodland 98629 La Center 98604 Venersborg 98649
Other ZIP codes in Cowlitz County
98581 98609 98611 98625 98626 98632 98645 98649 98674 All Cowlitz County frost dates · Washington 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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- Weekly yard to-dos
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.