Frost dates for ZIP 99588 (Mendeltna, AK)
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, Lake Susitna, AK (18 miles away).
- Average last spring frostMay 3050% chance of a 32°F freeze after this date
- Average first fall frostSep 450% chance of a 32°F freeze by this date
- Growing season (frost-free)95 daysmedian, 32°F threshold
- USDA hardiness zone2b-45 to -40°F avg. coldest night
Get The Dial for 99588 (Mendeltna)
Frost and freeze alerts from the NWS forecast for 99588, the spring soil-temperature heads-up for pre-emergent, and a short weekly yard-timing email.
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.
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 99588 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 early May.
Fertilizer window
Lawn region: North (cool-season). 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) | May 20 |
| 50% (the "average" last frost) | May 30 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 9 |
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) | Aug 17 |
| 50% (the "average" first frost) | Sep 4 |
| 90% (late: most years have frozen by now) | Sep 18 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | n/a | n/a |
| 32°F (freeze) | May 30 | Sep 4 |
| 28°F (hard freeze) | May 19 | Sep 17 |
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 99588
Dates count from your average last spring frost (May 30) and first fall frost (Sep 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 | Apr 4–18 | Jun 6–20 (transplant) | – |
| Pepper (sweet and hot) | Mar 21–Apr 4 | Jun 13–27 (transplant) | – |
| Eggplant | Mar 21–Apr 4 | Jun 13–27 (transplant) | – |
| Tomatillo | Apr 4–18 | Jun 6–20 (transplant) | – |
| Lettuce | Apr 4–18 | May 9–30 (transplant) May 2–Jun 13 (sow outdoors) | Jul 10–31 (transplant) Jun 26–Jul 24 (sowing) |
| Spinach | – | Apr 18–May 9 (sow outdoors) | Jul 10–31 (sowing) |
| Kale | Apr 4–18 | May 2–16 (transplant) May 2–16 (sow outdoors) | Jun 12–Jul 10 (transplant) May 29–Jun 26 (sowing) |
| Collards | Apr 4–18 | May 2–30 (transplant) May 2–30 (sow outdoors) | Jun 12–Jul 10 (transplant) |
| Broccoli | Mar 21–Apr 4 | May 2–16 (transplant) | May 29–Jun 26 (transplant) |
| Cabbage | Mar 21–Apr 4 | May 2–16 (transplant) | May 29–Jun 26 (transplant) |
| Cauliflower | Mar 21–Apr 4 | May 16–30 (transplant) | – |
| Brussels sprouts | Mar 7–21 | May 2–16 (transplant) | – |
| Kohlrabi | Apr 4–18 | May 2–16 (transplant) May 2–16 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Bok choy / Asian greens | – | May 2–16 (sow outdoors) | Jul 10–24 (sowing) |
| Arugula | – | May 2–30 (sow outdoors) | Jul 10–Aug 7 (sowing) |
| Mustard greens | – | May 2–23 (sow outdoors) | Jul 10–24 (sowing) |
| Swiss chard | Apr 18–May 2 | May 16–Jun 6 (transplant) May 16–Jun 13 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Beet | – | May 2–30 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Carrot | – | May 9–Jun 6 (sow outdoors) | Jun 12–26 (sowing) |
| Radish | – | Apr 25–Jun 6 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Turnip | – | May 2–23 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Parsnip | – | May 9–30 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 4–May 2 (sow outdoors) | Jun 12–26 (sowing) |
| Onion (bulbing) | Mar 7–21 | Apr 18–May 2 (transplant) | – |
| Green onion / scallion | – | Apr 18–May 16 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Leek | Mar 7–21 | May 2–16 (transplant) | – |
| Garlic | – | – | Jul 24–Aug 21 (sowing) |
| Shallot | – | Apr 18–May 2 (transplant) | Jul 24–Aug 21 (sowing) |
| Potato | – | May 2–16 (transplant) | – |
| Sweet potato | – | Jun 20–Jul 4 (transplant) | – |
| Sweet corn | – | Jun 6–20 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 6–20 (sow outdoors) | – |
| Bean, pole | – | Jun 6–20 (sow outdoors) | – |
| Lima bean | – | Jun 13–27 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 20–Jul 11 (sow outdoors) | – |
| Cucumber | May 2–9 | Jun 6–20 (transplant) Jun 6–20 (sow outdoors) | – |
| Summer squash / zucchini | May 2–9 | Jun 6–20 (transplant) Jun 6–20 (sow outdoors) | – |
| Winter squash | May 2–9 | Jun 6–20 (transplant) Jun 6–20 (sow outdoors) | – |
| Pumpkin | – | Jun 6–20 (sow outdoors) | – |
| Watermelon | May 2–9 | Jun 13–27 (transplant) Jun 13–27 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 2–9 | Jun 13–27 (transplant) Jun 13–27 (sow outdoors) | – |
| Okra | Apr 18–May 2 | Jun 13–27 (transplant) Jun 13–27 (sow outdoors) | – |
| Celery | Mar 7–21 | Jun 6–13 (transplant) | – |
| Basil | Apr 18–May 2 | Jun 6–20 (transplant) Jun 6–20 (sow outdoors) | – |
| Cilantro | – | May 16–Jun 13 (sow outdoors) | Jul 10–24 (sowing) |
| Parsley | Mar 21–Apr 4 | May 16–30 (transplant) May 9–30 (sow outdoors) | – |
| Dill | – | May 30–Jun 13 (sow outdoors) | Jul 10–24 (sowing) |
| Sunflower | – | May 30–Jun 13 (sow outdoors) | – |
| Asparagus (crowns) | – | May 2–16 (transplant) | – |
| Rhubarb (crowns) | – | May 2–16 (transplant) | – |
| Strawberry (plants) | – | May 2–16 (transplant) | Jun 26–Jul 24 (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: Lake Susitna, AK (NOAA GHCN-Daily ID USC00505397), elevation 2,375 ft, 17.6 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Glennallen 64 N, AK | 44 mi | Jun 5 | Aug 24 |
| Gulkana AP, AK | 55 mi | Jun 7 | Aug 21 |
The average last-frost dates of these stations span 8 days, a rough guide to local variation. See data sources & methods.
Frost questions for 99588
When is the last frost in 99588?
The average (50% chance) last spring freeze of 32°F for ZIP 99588 is May 30. For a more cautious planting date, use June 9, when only 1 year in 10 still sees a later freeze.
When is the first frost in 99588?
The average first fall freeze is September 4. In 1 year in 10 it comes by August 17.
What hardiness zone is 99588?
ZIP 99588 is in USDA zone 2b (-45 to -40°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 99588 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
99729 Cantwell 99737 Deltana 99586 Chistochina 99573 Kenny Lake 99674 Glacier View 99676 Chase 99645 Knik River 99755 Denali Park
Other ZIP codes in Copper River Census Area
99566 99573 99586 All Copper River Census Area frost dates · Alaska frost dates
Never miss a frost: get The Dial
Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
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.