Fall in zone 8bPhoto: George Chernilevsky, Public domain, via Wikimedia Commons
Frost dates for ZIP 98027 (Mirrormont, 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, Snoqualmie Falls, WA (8 miles away).
- Average last spring frostMar 3050% chance of a 32°F freeze after this date
- Average first fall frostNov 750% chance of a 32°F freeze by this date
- Growing season (frost-free)223 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 98027 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
Prune now
No frost-timed pruning windows are open this week.
Your average first frost is Nov 7: 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 4 |
| 50% (the "average" last frost) | Mar 30 |
| 10% (cautious: only 1 year in 10 freezes later) | Apr 21 |
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 22 |
| 50% (the "average" first frost) | Nov 7 |
| 90% (late: most years have frozen by now) | Dec 1 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Apr 26 | Oct 22 |
| 32°F (freeze) | Mar 30 | Nov 7 |
| 28°F (hard freeze) | Feb 27 | Nov 29 |
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 98027
Dates count from your average last spring frost (Mar 30) and first fall frost (Nov 7). 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 2–16 | Apr 6–20 (transplant) | Jul 11–Aug 8 (transplant) |
| Pepper (sweet and hot) | Jan 19–Feb 2 | Apr 13–27 (transplant) | Jul 18–Aug 8 (transplant) |
| Eggplant | Jan 19–Feb 2 | Apr 13–27 (transplant) | Jul 18–Aug 8 (transplant) |
| Tomatillo | Feb 2–16 | Apr 6–20 (transplant) | – |
| Lettuce | Feb 2–16 | Mar 9–30 (transplant) Mar 2–Apr 13 (sow outdoors) | Sep 12–Oct 3 (transplant) Aug 29–Sep 26 (sowing) |
| Spinach | – | Feb 16–Mar 9 (sow outdoors) | Sep 12–Oct 3 (sowing) |
| Kale | Feb 2–16 | Mar 2–16 (transplant) Mar 2–16 (sow outdoors) | Aug 15–Sep 12 (transplant) Aug 1–29 (sowing) |
| Collards | Feb 2–16 | Mar 2–30 (transplant) Mar 2–30 (sow outdoors) | Aug 15–Sep 12 (transplant) Aug 1–29 (sowing) |
| Broccoli | Jan 19–Feb 2 | Mar 2–16 (transplant) | Aug 1–29 (transplant) |
| Cabbage | Jan 19–Feb 2 | Mar 2–16 (transplant) | Aug 1–29 (transplant) |
| Cauliflower | Jan 19–Feb 2 | Mar 16–30 (transplant) | Aug 1–29 (transplant) |
| Brussels sprouts | Jan 5–19 | Mar 2–16 (transplant) | Jul 18–Aug 8 (transplant) |
| Kohlrabi | Feb 2–16 | Mar 2–16 (transplant) Mar 2–16 (sow outdoors) | Aug 29–Sep 12 (sowing) |
| Bok choy / Asian greens | – | Mar 2–16 (sow outdoors) | Sep 12–26 (sowing) |
| Arugula | – | Mar 2–30 (sow outdoors) | Sep 12–Oct 10 (sowing) |
| Mustard greens | – | Mar 2–23 (sow outdoors) | Sep 12–26 (sowing) |
| Swiss chard | Feb 16–Mar 2 | Mar 16–Apr 6 (transplant) Mar 16–Apr 13 (sow outdoors) | Aug 29–Sep 12 (sowing) |
| Beet | – | Mar 2–30 (sow outdoors) | Aug 29–Sep 12 (sowing) |
| Carrot | – | Mar 9–Apr 6 (sow outdoors) | Aug 15–29 (sowing) |
| Radish | – | Feb 23–Apr 6 (sow outdoors) | Sep 26–Oct 10 (sowing) |
| Turnip | – | Mar 2–23 (sow outdoors) | Aug 29–Sep 12 (sowing) |
| Parsnip | – | Mar 9–30 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Feb 2–Mar 2 (sow outdoors) | Aug 15–29 (sowing) |
| Onion (bulbing) | Jan 5–19 | Feb 16–Mar 2 (transplant) | – |
| Green onion / scallion | – | Feb 16–Mar 16 (sow outdoors) | Aug 29–Sep 12 (sowing) |
| Leek | Jan 5–19 | Mar 2–16 (transplant) | – |
| Garlic | – | – | Sep 26–Oct 24 (sowing) |
| Shallot | – | Feb 16–Mar 2 (transplant) | Sep 26–Oct 24 (sowing) |
| Potato | – | Mar 2–16 (transplant) | Jul 18–Aug 1 (transplant) |
| Sweet potato | – | Apr 20–May 4 (transplant) | – |
| Sweet corn | – | Apr 6–20 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 6–20 (sow outdoors) | Aug 15–29 (sowing) |
| Bean, pole | – | Apr 6–20 (sow outdoors) | – |
| Lima bean | – | Apr 13–27 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Apr 20–May 11 (sow outdoors) | – |
| Cucumber | Mar 2–9 | Apr 6–20 (transplant) Apr 6–20 (sow outdoors) | Aug 15–29 (sowing) |
| Summer squash / zucchini | Mar 2–9 | Apr 6–20 (transplant) Apr 6–20 (sow outdoors) | Aug 15–29 (sowing) |
| Winter squash | Mar 2–9 | Apr 6–20 (transplant) Apr 6–20 (sow outdoors) | – |
| Pumpkin | – | Apr 6–20 (sow outdoors) | – |
| Watermelon | Mar 2–9 | Apr 13–27 (transplant) Apr 13–27 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 2–9 | Apr 13–27 (transplant) Apr 13–27 (sow outdoors) | – |
| Okra | Feb 16–Mar 2 | Apr 13–27 (transplant) Apr 13–27 (sow outdoors) | – |
| Celery | Jan 5–19 | Apr 6–13 (transplant) | – |
| Basil | Feb 16–Mar 2 | Apr 6–20 (transplant) Apr 6–20 (sow outdoors) | – |
| Cilantro | – | Mar 16–Apr 13 (sow outdoors) | Sep 12–26 (sowing) |
| Parsley | Jan 19–Feb 2 | Mar 16–30 (transplant) Mar 9–30 (sow outdoors) | – |
| Dill | – | Mar 30–Apr 13 (sow outdoors) | Sep 12–26 (sowing) |
| Sunflower | – | Mar 30–Apr 13 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 2–16 (transplant) | – |
| Rhubarb (crowns) | – | Mar 2–16 (transplant) | – |
| Strawberry (plants) | – | Mar 2–16 (transplant) | Aug 29–Sep 26 (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: Snoqualmie Falls, WA (NOAA GHCN-Daily ID USC00457773), elevation 440 ft, 7.6 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Landsburg, WA | 10 mi | Apr 20 | Oct 25 |
| Renton Muni AP, WA | 10 mi | Mar 13 | Nov 16 |
| Cedar Lake, WA | 13 mi | Apr 23 | Nov 1 |
The average last-frost dates of these stations span 41 days, a rough guide to local variation. See data sources & methods.
Frost questions for 98027
When is the last frost in 98027?
The average (50% chance) last spring freeze of 32°F for ZIP 98027 is March 30. For a more cautious planting date, use April 21, when only 1 year in 10 still sees a later freeze.
When is the first frost in 98027?
The average first fall freeze is November 7. In 1 year in 10 it comes by October 22.
What hardiness zone is 98027?
ZIP 98027 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 98027 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
98029 Issaquah 98050 98075 Sammamish 98025 98024 Fall City 98059 East Renton Highlands 98038 Hobart 98074 Sammamish
Other ZIP codes in King County
98001 98002 98003 98004 98005 98006 98007 98008 98010 98011 98014 98019 98022 98023 98024 98025 98028 98029 98030 98031 98032 98033 98034 98038 All King 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.