Fall in zone 6bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 97603 (Altamont, OR)
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, Klamath Falls Intl AP, OR (3 miles away).
- Average last spring frostJun 950% chance of a 32°F freeze after this date
- Average first fall frostSep 1850% chance of a 32°F freeze by this date
- Growing season (frost-free)99 daysmedian, 32°F threshold
- USDA hardiness zone6b-5 to 0°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 97603 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
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 22 |
| 50% (the "average" last frost) | Jun 9 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 26 |
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) | Sep 4 |
| 50% (the "average" first frost) | Sep 18 |
| 90% (late: most years have frozen by now) | Oct 1 |
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) | Jun 9 | Sep 18 |
| 28°F (hard freeze) | May 21 | Oct 2 |
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 97603
Dates count from your average last spring frost (Jun 9) and first fall frost (Sep 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 | Apr 14–28 | Jun 16–30 (transplant) | – |
| Pepper (sweet and hot) | Mar 31–Apr 14 | Jun 23–Jul 7 (transplant) | – |
| Eggplant | Mar 31–Apr 14 | Jun 23–Jul 7 (transplant) | – |
| Tomatillo | Apr 14–28 | Jun 16–30 (transplant) | – |
| Lettuce | Apr 14–28 | May 19–Jun 9 (transplant) May 12–Jun 23 (sow outdoors) | Jul 24–Aug 14 (transplant) Jul 10–Aug 7 (sowing) |
| Spinach | – | Apr 28–May 19 (sow outdoors) | Jul 24–Aug 14 (sowing) |
| Kale | Apr 14–28 | May 12–26 (transplant) May 12–26 (sow outdoors) | Jun 26–Jul 24 (transplant) Jun 12–Jul 10 (sowing) |
| Collards | Apr 14–28 | May 12–Jun 9 (transplant) May 12–Jun 9 (sow outdoors) | Jun 26–Jul 24 (transplant) Jun 12–Jul 10 (sowing) |
| Broccoli | Mar 31–Apr 14 | May 12–26 (transplant) | Jun 12–Jul 10 (transplant) |
| Cabbage | Mar 31–Apr 14 | May 12–26 (transplant) | Jun 12–Jul 10 (transplant) |
| Cauliflower | Mar 31–Apr 14 | May 26–Jun 9 (transplant) | Jun 12–Jul 10 (transplant) |
| Brussels sprouts | Mar 17–31 | May 12–26 (transplant) | May 29–Jun 19 (transplant) |
| Kohlrabi | Apr 14–28 | May 12–26 (transplant) May 12–26 (sow outdoors) | Jul 10–24 (sowing) |
| Bok choy / Asian greens | – | May 12–26 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Arugula | – | May 12–Jun 9 (sow outdoors) | Jul 24–Aug 21 (sowing) |
| Mustard greens | – | May 12–Jun 2 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Swiss chard | Apr 28–May 12 | May 26–Jun 16 (transplant) May 26–Jun 23 (sow outdoors) | Jul 10–24 (sowing) |
| Beet | – | May 12–Jun 9 (sow outdoors) | Jul 10–24 (sowing) |
| Carrot | – | May 19–Jun 16 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Radish | – | May 5–Jun 16 (sow outdoors) | Aug 7–21 (sowing) |
| Turnip | – | May 12–Jun 2 (sow outdoors) | Jul 10–24 (sowing) |
| Parsnip | – | May 19–Jun 9 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 14–May 12 (sow outdoors) | Jun 26–Jul 10 (sowing) |
| Onion (bulbing) | Mar 17–31 | Apr 28–May 12 (transplant) | – |
| Green onion / scallion | – | Apr 28–May 26 (sow outdoors) | Jul 10–24 (sowing) |
| Leek | Mar 17–31 | May 12–26 (transplant) | – |
| Garlic | – | – | Aug 7–Sep 4 (sowing) |
| Shallot | – | Apr 28–May 12 (transplant) | Aug 7–Sep 4 (sowing) |
| Potato | – | May 12–26 (transplant) | May 29–Jun 12 (transplant) |
| Sweet potato | – | Jun 30–Jul 14 (transplant) | – |
| Sweet corn | – | Jun 16–30 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 16–30 (sow outdoors) | – |
| Bean, pole | – | Jun 16–30 (sow outdoors) | – |
| Lima bean | – | Jun 23–Jul 7 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 30–Jul 21 (sow outdoors) | – |
| Cucumber | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Summer squash / zucchini | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Winter squash | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Pumpkin | – | Jun 16–30 (sow outdoors) | – |
| Watermelon | May 12–19 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 12–19 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Okra | Apr 28–May 12 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Celery | Mar 17–31 | Jun 16–23 (transplant) | – |
| Basil | Apr 28–May 12 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Cilantro | – | May 26–Jun 23 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Parsley | Mar 31–Apr 14 | May 26–Jun 9 (transplant) May 19–Jun 9 (sow outdoors) | – |
| Dill | – | Jun 9–23 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Sunflower | – | Jun 9–23 (sow outdoors) | – |
| Asparagus (crowns) | – | May 12–26 (transplant) | – |
| Rhubarb (crowns) | – | May 12–26 (transplant) | – |
| Strawberry (plants) | – | May 12–26 (transplant) | Jul 10–Aug 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: Klamath Falls Intl AP, OR (NOAA GHCN-Daily ID USW00094236), elevation 4,084 ft, 3.2 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Keno, OR | 12 mi | Jun 5 | Sep 20 |
| Tulelake, CA | 15 mi | Jun 6 | Sep 14 |
| Gerber Dam, OR | 28 mi | May 31 | Sep 21 |
The average last-frost dates of these stations span 9 days, a rough guide to local variation. See data sources & methods.
Frost questions for 97603
When is the last frost in 97603?
The average (50% chance) last spring freeze of 32°F for ZIP 97603 is June 9. For a more cautious planting date, use June 26, when only 1 year in 10 still sees a later freeze.
When is the first frost in 97603?
The average first fall freeze is September 18. In 1 year in 10 it comes by September 4.
What hardiness zone is 97603?
ZIP 97603 is in USDA zone 6b (-5 to 0°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 97603 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
97634 97633 Merrill 97625 97632 Malin 97623 Bonanza 97627 Keno 96023 Dorris 97639 Sprague River
Other ZIP codes in Klamath County
97601 97604 97621 97622 97623 97624 97625 97626 97627 97632 97633 97634 97639 97731 97733 97737 All Klamath County frost dates · Oregon frost dates
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- 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.