Frost dates for ZIP 99346 (Benton 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, Mcnary Dam, WA (6 miles away).
- Average last spring frostMar 2750% chance of a 32°F freeze after this date
- Average first fall frostNov 450% chance of a 32°F freeze by this date
- Growing season (frost-free)221 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 17, 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 99346 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
Prune now
No frost-timed pruning windows are open this week.
Your average first frost is Nov 4: 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 8 |
| 50% (the "average" last frost) | Mar 27 |
| 10% (cautious: only 1 year in 10 freezes later) | Apr 14 |
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 21 |
| 50% (the "average" first frost) | Nov 4 |
| 90% (late: most years have frozen by now) | Nov 22 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Apr 15 | Oct 24 |
| 32°F (freeze) | Mar 27 | Nov 4 |
| 28°F (hard freeze) | Mar 6 | Nov 18 |
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 99346
Dates count from your average last spring frost (Mar 27) and first fall frost (Nov 4). 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 30–Feb 13 | Apr 3–17 (transplant) | Jul 8–Aug 5 (transplant) |
| Pepper (sweet and hot) | Jan 16–30 | Apr 10–24 (transplant) | Jul 15–Aug 5 (transplant) |
| Eggplant | Jan 16–30 | Apr 10–24 (transplant) | Jul 15–Aug 5 (transplant) |
| Tomatillo | Jan 30–Feb 13 | Apr 3–17 (transplant) | – |
| Lettuce | Jan 30–Feb 13 | Mar 6–27 (transplant) Feb 27–Apr 10 (sow outdoors) | Sep 9–30 (transplant) Aug 26–Sep 23 (sowing) |
| Spinach | – | Feb 13–Mar 6 (sow outdoors) | Sep 9–30 (sowing) |
| Kale | Jan 30–Feb 13 | Feb 27–Mar 13 (transplant) Feb 27–Mar 13 (sow outdoors) | Aug 12–Sep 9 (transplant) Jul 29–Aug 26 (sowing) |
| Collards | Jan 30–Feb 13 | Feb 27–Mar 27 (transplant) Feb 27–Mar 27 (sow outdoors) | Aug 12–Sep 9 (transplant) Jul 29–Aug 26 (sowing) |
| Broccoli | Jan 16–30 | Feb 27–Mar 13 (transplant) | Jul 29–Aug 26 (transplant) |
| Cabbage | Jan 16–30 | Feb 27–Mar 13 (transplant) | Jul 29–Aug 26 (transplant) |
| Cauliflower | Jan 16–30 | Mar 13–27 (transplant) | Jul 29–Aug 26 (transplant) |
| Brussels sprouts | Jan 2–16 | Feb 27–Mar 13 (transplant) | Jul 15–Aug 5 (transplant) |
| Kohlrabi | Jan 30–Feb 13 | Feb 27–Mar 13 (transplant) Feb 27–Mar 13 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Bok choy / Asian greens | – | Feb 27–Mar 13 (sow outdoors) | Sep 9–23 (sowing) |
| Arugula | – | Feb 27–Mar 27 (sow outdoors) | Sep 9–Oct 7 (sowing) |
| Mustard greens | – | Feb 27–Mar 20 (sow outdoors) | Sep 9–23 (sowing) |
| Swiss chard | Feb 13–27 | Mar 13–Apr 3 (transplant) Mar 13–Apr 10 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Beet | – | Feb 27–Mar 27 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Carrot | – | Mar 6–Apr 3 (sow outdoors) | Aug 12–26 (sowing) |
| Radish | – | Feb 20–Apr 3 (sow outdoors) | Sep 23–Oct 7 (sowing) |
| Turnip | – | Feb 27–Mar 20 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Parsnip | – | Mar 6–27 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Jan 30–Feb 27 (sow outdoors) | Aug 12–26 (sowing) |
| Onion (bulbing) | Jan 2–16 | Feb 13–27 (transplant) | – |
| Green onion / scallion | – | Feb 13–Mar 13 (sow outdoors) | Aug 26–Sep 9 (sowing) |
| Leek | Jan 2–16 | Feb 27–Mar 13 (transplant) | – |
| Garlic | – | – | Sep 23–Oct 21 (sowing) |
| Shallot | – | Feb 13–27 (transplant) | Sep 23–Oct 21 (sowing) |
| Potato | – | Feb 27–Mar 13 (transplant) | Jul 15–29 (transplant) |
| Sweet potato | – | Apr 17–May 1 (transplant) | – |
| Sweet corn | – | Apr 3–17 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 3–17 (sow outdoors) | Aug 12–26 (sowing) |
| Bean, pole | – | Apr 3–17 (sow outdoors) | – |
| Lima bean | – | Apr 10–24 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Apr 17–May 8 (sow outdoors) | – |
| Cucumber | Feb 27–Mar 6 | Apr 3–17 (transplant) Apr 3–17 (sow outdoors) | Aug 12–26 (sowing) |
| Summer squash / zucchini | Feb 27–Mar 6 | Apr 3–17 (transplant) Apr 3–17 (sow outdoors) | Aug 12–26 (sowing) |
| Winter squash | Feb 27–Mar 6 | Apr 3–17 (transplant) Apr 3–17 (sow outdoors) | – |
| Pumpkin | – | Apr 3–17 (sow outdoors) | – |
| Watermelon | Feb 27–Mar 6 | Apr 10–24 (transplant) Apr 10–24 (sow outdoors) | – |
| Cantaloupe / muskmelon | Feb 27–Mar 6 | Apr 10–24 (transplant) Apr 10–24 (sow outdoors) | – |
| Okra | Feb 13–27 | Apr 10–24 (transplant) Apr 10–24 (sow outdoors) | – |
| Celery | Jan 2–16 | Apr 3–10 (transplant) | – |
| Basil | Feb 13–27 | Apr 3–17 (transplant) Apr 3–17 (sow outdoors) | – |
| Cilantro | – | Mar 13–Apr 10 (sow outdoors) | Sep 9–23 (sowing) |
| Parsley | Jan 16–30 | Mar 13–27 (transplant) Mar 6–27 (sow outdoors) | – |
| Dill | – | Mar 27–Apr 10 (sow outdoors) | Sep 9–23 (sowing) |
| Sunflower | – | Mar 27–Apr 10 (sow outdoors) | – |
| Asparagus (crowns) | – | Feb 27–Mar 13 (transplant) | – |
| Rhubarb (crowns) | – | Feb 27–Mar 13 (transplant) | – |
| Strawberry (plants) | – | Feb 27–Mar 13 (transplant) | Aug 26–Sep 23 (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: Mcnary Dam, WA (NOAA GHCN-Daily ID USC00455231), elevation 361 ft, 6.2 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Mcnary Dam #2, OR | 7 mi | Mar 30 | Nov 4 |
| Hermiston 2 NW, OR | 12 mi | Apr 27 | Oct 7 |
| Hermiston Muni AP, OR | 14 mi | Apr 26 | Oct 10 |
The average last-frost dates of these stations span 31 days, a rough guide to local variation. See data sources & methods.
Frost questions for 99346
When is the last frost in 99346?
The average (50% chance) last spring freeze of 32°F for ZIP 99346 is March 27. For a more cautious planting date, use April 14, when only 1 year in 10 still sees a later freeze.
When is the first frost in 99346?
The average first fall freeze is November 4. In 1 year in 10 it comes by October 21.
What hardiness zone is 99346?
ZIP 99346 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 99346 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
97882 Umatilla 99337 Finley 99338 Kennewick 97838 Hermiston 99336 Kennewick 99352 Richland 97844 Irrigon 97875 Stanfield
Other ZIP codes in Benton County
98944 99320 99336 99337 99338 99345 99350 99352 99353 99354 All Benton County frost dates · Washington frost dates
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