USDA Hardiness Zone 8b
Frost Dates for 98579 — Rochester, Washington
NOAA 1991–2020 normals from Centralia, WA (185 ft), 9 miles southeast.
Updated
In Rochester, the last spring frost (32°F) is around April 22 in half of years and has passed by May 10 in nine years out of ten. The first fall frost comes around October 27, as early as October 7 one year in ten, leaving a typical freeze-free season of 188 days (NOAA, Centralia, WA).
- Last spring frost
- April 22
- First fall frost
- October 27
- Growing season
- 188 days
- Hardiness zone
- 8b
50% probability
50% probability
freeze-free, 50%
15 to 20°F (-9.4 to -6.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 25%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
5 of 20 observed
NOAA normal
Frost risk by date in Rochester
Half of springs at Centralia, WA see their last 32°F night by April 22; only one in ten is past it by March 30, and one in ten still has one after May 10. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 4 20%, and after May 10 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 56% of the 113 Washington stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 27 in half of years, as early as October 7 one year in ten, and holds off past November 17 one year in ten. A hard freeze of 28°F follows 17 days later, around November 13; in spring the one-in-ten date for 28°F is April 17, 23 days before the 32°F one. The freeze-free season lasts 188 days in a typical year, shorter than at 51% of the 113 Washington stations; it reaches 215 days one year in ten and falls short of 163 one year in ten. On average 48 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 15 days longer, to about May 7, and return around October 8. Nights of 24°F, cold enough to damage hardier plants, come in 98% of winters and 16°F in 47%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 24 | Apr 28 | May 1 | May 4 | May 7 | May 11 | May 14 | May 18 | May 24 |
| 32°F | Mar 30 | Apr 5 | Apr 12 | Apr 18 | Apr 22 | Apr 26 | Apr 30 | May 4 | May 10 |
| 28°F | Feb 24 | Mar 4 | Mar 12 | Mar 18 | Mar 23 | Mar 27 | Mar 31 | Apr 6 | Apr 17 |
| 24°F98% of yrs | Jan 2 | Jan 21 | Feb 3 | Feb 14 | Feb 20 | Feb 26 | Mar 2 | Mar 8 | Mar 17 |
| 20°F83% of yrs | Dec 10 | Dec 22 | Jan 2 | Jan 13 | Jan 27 | Feb 8 | Feb 17 | Feb 25 | Mar 4 |
| 16°F47% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 22 | Sep 29 | Oct 1 | Oct 5 | Oct 8 | Oct 13 | Oct 17 | Oct 21 | Oct 26 |
| 32°F | Oct 7 | Oct 15 | Oct 19 | Oct 23 | Oct 27 | Oct 31 | Nov 3 | Nov 8 | Nov 17 |
| 28°F | Oct 21 | Oct 30 | Nov 4 | Nov 8 | Nov 13 | Nov 17 | Nov 22 | Nov 28 | Dec 7 |
| 24°F98% of yrs | Nov 6 | Nov 13 | Nov 19 | Nov 25 | Nov 30 | Dec 6 | Dec 12 | Dec 21 | Jan 1 |
| 20°F83% of yrs | Nov 17 | Nov 27 | Dec 3 | Dec 9 | Dec 16 | Dec 23 | Jan 1 | Jan 12 | Feb 8 |
| 16°F47% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Centralia, WA, 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 98579 →Compare Rochester with another place →
Weather by month in Rochester
August is the warmest month at Centralia, WA, averaging 78°F by day and 53°F at night; December is the coldest at 45°F and 34°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 82% of years and May still brings one in 28% of years.
Warmth for growing adds up to 1,943 growing degree days a year (base 50°F), fewer than at 52% of the 113 Washington stations. 29% of them (559) have built up by the end of June, and August adds the most, 480. Precipitation totals 41.4 inches a year, most in November (6.5") and least in July (0.5"); May to September bring 16% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 46 | 34 | 5.9 | 100% | 10 | 2 |
| Feb | 50 | 34 | 4.2 | 99% | 10 | 4 |
| Mar | 54 | 36 | 4.4 | 100% | 7 | 14 |
| Apr | 60 | 39 | 3.2 | 82% | 3 | 53 |
| May | 67 | 44 | 2.4 | 28% | <1 | 183 |
| Jun | 71 | 49 | 1.5 | 0% | 0 | 303 |
| Jul | 78 | 53 | 0.5 | 0% | 0 | 471 |
| Aug | 78 | 53 | 0.8 | 0% | 0 | 480 |
| Sep | 73 | 48 | 1.6 | 2% | 0 | 316 |
| Oct | 61 | 43 | 4.0 | 62% | 1 | 101 |
| Nov | 51 | 37 | 6.5 | 98% | 6 | 13 |
| Dec | 45 | 34 | 6.4 | 100% | 11 | 2 |
Monthly normals 1991–2020 at Centralia, WA (185 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, Olympia Airport, WA, 14 miles northeast of Rochester, has a last frost 7 days later (April 29), a first frost 13 days earlier (October 14), a season 19 days shorter.
When it snows in Rochester, Washington
Measurable snow is rare here: only 5 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Centralia, WA, 9.1 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 98579
| When | What to do |
|---|---|
| February 11 – February 25 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 25 – March 11 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 25 – April 8 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 22 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 4 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 13 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 27 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 98579 is 9 miles from Centralia, WA, which stands at 185 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 98531 (Centralia). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98579 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Washington →
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.