USDA Hardiness Zone 6b
Frost Dates for 97603 — Klamath Falls, Oregon
NOAA 1991–2020 normals from Klamath Falls International Airport, OR (4,084 ft), 2 miles southwest.
Updated
In Klamath Falls, the last spring frost (32°F) is around June 9 in half of years and has passed by June 26 in nine years out of ten. The first fall frost comes around September 18, as early as September 4 one year in ten, leaving a typical freeze-free season of 99 days (NOAA, Klamath Falls International Airport, OR).
- Last spring frost
- June 9
- First fall frost
- September 18
- Growing season
- 99 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- November 18
- Last snow
- April 13
- Winters with snow
- 100%
- Snow per year
- 52.2"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Klamath Falls
Half of springs at Klamath Falls International Airport, OR see their last 32°F night by June 9; only one in ten is past it by May 22, and one in ten still has one after June 26. Planting tender crops after June 16 leaves a 30% risk of a frost on them, after June 21 20%, and after June 26 10%. The 17 days between the even-odds date and the one-in-ten date is narrower than at 83% of the 103 Oregon stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 18 in half of years, as early as September 4 one year in ten, and holds off past October 1 one year in ten. A hard freeze of 28°F follows 14 days later, around October 2; in spring the one-in-ten date for 28°F is June 12, 14 days before the 32°F one. The freeze-free season lasts 99 days in a typical year, shorter than at 96% of the 103 Oregon stations; it reaches 120 days one year in ten and falls short of 77 one year in ten. On average 184 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 13 and March 14.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 22 | May 30 | Jun 3 | Jun 6 | Jun 9 | Jun 12 | Jun 16 | Jun 21 | Jun 26 |
| 28°F | May 2 | May 8 | May 13 | May 16 | May 21 | May 26 | Jun 1 | Jun 5 | Jun 12 |
| 24°F | Apr 13 | Apr 19 | Apr 24 | Apr 28 | May 1 | May 3 | May 7 | May 12 | May 20 |
| 20°F | Mar 21 | Mar 30 | Apr 4 | Apr 8 | Apr 12 | Apr 16 | Apr 20 | Apr 25 | May 1 |
| 16°F | Feb 15 | Feb 25 | Mar 2 | Mar 8 | Mar 14 | Mar 20 | Mar 27 | Apr 3 | Apr 11 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Sep 4 | Sep 9 | Sep 13 | Sep 16 | Sep 18 | Sep 20 | Sep 23 | Sep 27 | Oct 1 |
| 28°F | Sep 17 | Sep 23 | Sep 26 | Sep 29 | Oct 2 | Oct 5 | Oct 7 | Oct 12 | Oct 17 |
| 24°F | Oct 2 | Oct 6 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Nov 1 |
| 20°F | Oct 14 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 2 | Nov 5 | Nov 10 | Nov 17 |
| 16°F | Oct 26 | Nov 1 | Nov 5 | Nov 10 | Nov 13 | Nov 18 | Nov 22 | Nov 28 | Dec 6 |
Freeze probabilities 1991–2020 at Klamath Falls International Airport, OR, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 97603 →Compare Klamath Falls with another place →
Weather by month in Klamath Falls
July is the warmest month at Klamath Falls International Airport, OR, averaging 86°F by day and 48°F at night; December is the coldest at 40°F and 21°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 74% of years.
Warmth for growing adds up to 1,747 growing degree days a year (base 50°F), fewer than at 77% of the 103 Oregon stations. 24% of them (418) have built up by the end of June, and July adds the most, 529. Precipitation totals 11.1 inches a year, most in December (1.8") and least in July (0.2"); May to September bring 23% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 42 | 22 | 1.5 | 100% | 28 | 0 |
| Feb | 46 | 24 | 1.1 | 100% | 25 | 0 |
| Mar | 52 | 27 | 1.0 | 100% | 25 | 2 |
| Apr | 58 | 29 | 1.1 | 100% | 21 | 19 |
| May | 67 | 36 | 1.0 | 100% | 9 | 122 |
| Jun | 76 | 41 | 0.7 | 74% | 2 | 276 |
| Jul | 86 | 48 | 0.2 | 4% | 0 | 529 |
| Aug | 85 | 47 | 0.3 | 6% | <1 | 486 |
| Sep | 78 | 39 | 0.3 | 87% | 3 | 262 |
| Oct | 64 | 31 | 0.7 | 100% | 19 | 50 |
| Nov | 49 | 25 | 1.4 | 100% | 24 | 3 |
| Dec | 40 | 21 | 1.8 | 100% | 28 | 0 |
Monthly normals 1991–2020 at Klamath Falls International Airport, OR (4,084 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Tulelake, CA, 19 miles southeast of Klamath Falls, has a last frost 3 days earlier (June 6), a first frost 4 days earlier (September 14), a season 2 days shorter.
When it snows in Klamath Falls, Oregon
The first measurable snow (0.1 inch or more) in Klamath Falls usually arrives around November 18, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Keno, OR, 11.4 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 57 days after the last snow.
Planting calendar for 97603
| When | What to do |
|---|---|
| March 31 – April 14 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 14 – April 28 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 12 – May 26 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 9 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 26 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 4 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 18 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 97603 is 2 miles from Klamath Falls International Airport, OR, which stands at 4,084 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97603 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.