Fall in zone 7bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 99338 (Kennewick, 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, Kennewick, WA (9 miles away).
- Average last spring frostMar 2850% chance of a 32°F freeze after this date
- Average first fall frostOct 3050% chance of a 32°F freeze by this date
- Growing season (frost-free)216 daysmedian, 32°F threshold
- USDA hardiness zone7b5 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
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 99338 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 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.
Your average first frost is Oct 30: 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 9 |
| 50% (the "average" last frost) | Mar 28 |
| 10% (cautious: only 1 year in 10 freezes later) | Apr 10 |
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 18 |
| 50% (the "average" first frost) | Oct 30 |
| 90% (late: most years have frozen by now) | Nov 15 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Apr 14 | Oct 21 |
| 32°F (freeze) | Mar 28 | Oct 30 |
| 28°F (hard freeze) | Mar 8 | Nov 11 |
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 99338
Dates count from your average last spring frost (Mar 28) and first fall frost (Oct 30). 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 | Jan 31–Feb 14 | Apr 4–18 (transplant) | Jul 3–31 (transplant) |
| Pepper (sweet and hot) | Jan 17–31 | Apr 11–25 (transplant) | Jul 10–31 (transplant) |
| Eggplant | Jan 17–31 | Apr 11–25 (transplant) | Jul 10–31 (transplant) |
| Tomatillo | Jan 31–Feb 14 | Apr 4–18 (transplant) | – |
| Lettuce | Jan 31–Feb 14 | Mar 7–28 (transplant) Feb 28–Apr 11 (sow outdoors) | Sep 4–25 (transplant) Aug 21–Sep 18 (sowing) |
| Spinach | – | Feb 14–Mar 7 (sow outdoors) | Sep 4–25 (sowing) |
| Kale | Jan 31–Feb 14 | Feb 28–Mar 14 (transplant) Feb 28–Mar 14 (sow outdoors) | Aug 7–Sep 4 (transplant) Jul 24–Aug 21 (sowing) |
| Collards | Jan 31–Feb 14 | Feb 28–Mar 28 (transplant) Feb 28–Mar 28 (sow outdoors) | Aug 7–Sep 4 (transplant) Jul 24–Aug 21 (sowing) |
| Broccoli | Jan 17–31 | Feb 28–Mar 14 (transplant) | Jul 24–Aug 21 (transplant) |
| Cabbage | Jan 17–31 | Feb 28–Mar 14 (transplant) | Jul 24–Aug 21 (transplant) |
| Cauliflower | Jan 17–31 | Mar 14–28 (transplant) | Jul 24–Aug 21 (transplant) |
| Brussels sprouts | Jan 3–17 | Feb 28–Mar 14 (transplant) | Jul 10–31 (transplant) |
| Kohlrabi | Jan 31–Feb 14 | Feb 28–Mar 14 (transplant) Feb 28–Mar 14 (sow outdoors) | Aug 21–Sep 4 (sowing) |
| Bok choy / Asian greens | – | Feb 28–Mar 14 (sow outdoors) | Sep 4–18 (sowing) |
| Arugula | – | Feb 28–Mar 28 (sow outdoors) | Sep 4–Oct 2 (sowing) |
| Mustard greens | – | Feb 28–Mar 21 (sow outdoors) | Sep 4–18 (sowing) |
| Swiss chard | Feb 14–28 | Mar 14–Apr 4 (transplant) Mar 14–Apr 11 (sow outdoors) | Aug 21–Sep 4 (sowing) |
| Beet | – | Feb 28–Mar 28 (sow outdoors) | Aug 21–Sep 4 (sowing) |
| Carrot | – | Mar 7–Apr 4 (sow outdoors) | Aug 7–21 (sowing) |
| Radish | – | Feb 21–Apr 4 (sow outdoors) | Sep 18–Oct 2 (sowing) |
| Turnip | – | Feb 28–Mar 21 (sow outdoors) | Aug 21–Sep 4 (sowing) |
| Parsnip | – | Mar 7–28 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Jan 31–Feb 28 (sow outdoors) | Aug 7–21 (sowing) |
| Onion (bulbing) | Jan 3–17 | Feb 14–28 (transplant) | – |
| Green onion / scallion | – | Feb 14–Mar 14 (sow outdoors) | Aug 21–Sep 4 (sowing) |
| Leek | Jan 3–17 | Feb 28–Mar 14 (transplant) | – |
| Garlic | – | – | Sep 18–Oct 16 (sowing) |
| Shallot | – | Feb 14–28 (transplant) | Sep 18–Oct 16 (sowing) |
| Potato | – | Feb 28–Mar 14 (transplant) | Jul 10–24 (transplant) |
| Sweet potato | – | Apr 18–May 2 (transplant) | – |
| Sweet corn | – | Apr 4–18 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 4–18 (sow outdoors) | Aug 7–21 (sowing) |
| Bean, pole | – | Apr 4–18 (sow outdoors) | – |
| Lima bean | – | Apr 11–25 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Apr 18–May 9 (sow outdoors) | – |
| Cucumber | Feb 28–Mar 7 | Apr 4–18 (transplant) Apr 4–18 (sow outdoors) | Aug 7–21 (sowing) |
| Summer squash / zucchini | Feb 28–Mar 7 | Apr 4–18 (transplant) Apr 4–18 (sow outdoors) | Aug 7–21 (sowing) |
| Winter squash | Feb 28–Mar 7 | Apr 4–18 (transplant) Apr 4–18 (sow outdoors) | – |
| Pumpkin | – | Apr 4–18 (sow outdoors) | – |
| Watermelon | Feb 28–Mar 7 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | – |
| Cantaloupe / muskmelon | Feb 28–Mar 7 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | – |
| Okra | Feb 14–28 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | – |
| Celery | Jan 3–17 | Apr 4–11 (transplant) | – |
| Basil | Feb 14–28 | Apr 4–18 (transplant) Apr 4–18 (sow outdoors) | – |
| Cilantro | – | Mar 14–Apr 11 (sow outdoors) | Sep 4–18 (sowing) |
| Parsley | Jan 17–31 | Mar 14–28 (transplant) Mar 7–28 (sow outdoors) | – |
| Dill | – | Mar 28–Apr 11 (sow outdoors) | Sep 4–18 (sowing) |
| Sunflower | – | Mar 28–Apr 11 (sow outdoors) | – |
| Asparagus (crowns) | – | Feb 28–Mar 14 (transplant) | – |
| Rhubarb (crowns) | – | Feb 28–Mar 14 (transplant) | – |
| Strawberry (plants) | – | Feb 28–Mar 14 (transplant) | Aug 21–Sep 18 (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: Kennewick, WA (NOAA GHCN-Daily ID USC00454154), elevation 390 ft, 8.6 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Richland, WA | 10 mi | Apr 6 | Oct 24 |
| Pasco Tri Cities AP, WA | 10 mi | Apr 27 | Oct 11 |
| Mcnary Dam, WA | 16 mi | Mar 27 | Nov 4 |
The average last-frost dates of these stations span 31 days, a rough guide to local variation. See data sources & methods.
Frost questions for 99338
When is the last frost in 99338?
The average (50% chance) last spring freeze of 32°F for ZIP 99338 is March 28. For a more cautious planting date, use April 10, when only 1 year in 10 still sees a later freeze.
When is the first frost in 99338?
The average first fall freeze is October 30. In 1 year in 10 it comes by October 18.
What hardiness zone is 99338?
ZIP 99338 is in USDA zone 7b (5 to 10°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 99338 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
99352 Richland 99336 Kennewick 99346 99354 Richland 99353 West Richland 99337 Finley 99320 Benton City 97882 Umatilla
Other ZIP codes in Benton County
98944 99320 99336 99337 99345 99346 99350 99352 99353 99354 All Benton 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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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.