When is the last frost in Princeton, OR?

For ZIP code 97721, the average last spring frost (32°F) is June 11, based on NOAA 1991-2020 climate normals for the O O Rch, OR weather station. There is a 1-in-10 chance of a frost after July 1.

When is the first frost in Princeton, OR?

The average first fall frost (32°F) is September 6. There is a 1-in-10 chance of frost by August 19, so tender plants are at risk from that point on.

How long is the growing season in 97721?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 88 days long.

Are these frost dates a forecast?

No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.

Frost dates for 97721Princeton, OR

The average last spring frost in Princeton is June 11 and the average first fall frost is September 6, giving a typical growing season of about 88 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 11
Average first fall frost: Sep 6
Growing season: 88 days

Frost risk by date

NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.

Spring dates: chance of a frost AFTER the date. Fall dates: chance of a frost BEFORE the date.
Temperature	Last spring: 90% / 50% / 10% chance	First fall: 10% / 50% / 90% chance	Growing season (50%)	Years with at least one
Light frost (36°F)	—	—	59 days	100%
Frost / freeze (32°F)	May 18 · Jun 11 · Jul 1	Aug 19 · Sep 6 · Sep 22	88 days	100%
Hard freeze (28°F)	Apr 29 · May 22 · Jun 20	Sep 3 · Sep 19 · Oct 7	122 days	100%

Where these dates come from

ZIP code 97721 is matched to the NOAA station O O Rch, OR, 34.8 km away, at 4,136 ft elevation (913 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
O O Rch, OR (used)	4,136 ft	Jun 11	Sep 6
Malheur Refuge Hq, OR	4,118 ft	May 29	Sep 18
Burns Muni Ap, OR	4,140 ft	Jun 11	Sep 6
Hart Mtn Refuge, OR	5,618 ft	—	—

Frost dates near Princeton

Diamond, OR 97722 · last May 29, first Sep 18
Frenchglen, OR 97736 · last May 10, first Oct 7
Burns, OR 97720 · last Jun 11, first Sep 6
Hines, OR 97738 · last Jun 11, first Sep 6
Crane, OR 97732 · last Jun 11, first Sep 6
Riley, OR 97758 · last Jun 11, first Sep 28
Plush, OR 97637 · last Jun 6, first Sep 14
Riverside, OR 97917 · last Jun 7, first Sep 6

Frequently asked questions

When is the last frost in Princeton, OR?: For ZIP code 97721, the average last spring frost (32°F) is June 11, based on NOAA 1991-2020 climate normals for the O O Rch, OR weather station. There is a 1-in-10 chance of a frost after July 1.
When is the first frost in Princeton, OR?: The average first fall frost (32°F) is September 6. There is a 1-in-10 chance of frost by August 19, so tender plants are at risk from that point on.
How long is the growing season in 97721?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 88 days long.
Are these frost dates a forecast?: No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.