Do I need to cover plants for frost in Portland, OR this week?
Here's the next 7 days for covering plants in Portland, checked hour by hour against the published thresholds. Below it: what Portland's 1991–2020 climate averages say about the months that usually work.
This week in Portland
Asking the sky…
Fairsky is not a substitute for official warnings. For warnings, go to weather.gov. Verdicts are guidance, not guarantees. Your product's label always wins.
When covering plants usually works in Portland
- On 1991–2020 averages, Portland's median last spring freeze (32°F) comes around February 25 and the median first fall freeze around December 1. In half of years the date is later than that, in half earlier.
- Nights of 36°F or colder, when frost can form under clear, calm skies, typically end around March 29 and return around November 12.
- Hard freezes (28°F or colder, which kill most tender plants even under a cover) typically end around January 31 and return around December 20.
- Portland averages 18 nights a year at or below 32°F, most of them in January (5.4).
| Month | Avg high | Avg low | Days ≥0.10" rain | Nights ≤32°F |
|---|---|---|---|---|
| January | 47° | 37° | 13.8 | 5.4 |
| February | 51° | 39° | 10.3 | 3.6 |
| March | 56° | 41° | 12.1 | 1.0 |
| April | 61° | 44° | 10.5 | 0.0 |
| May | 68° | 49° | 7.5 | 0.0 |
| June | 73° | 53° | 4.9 | 0.0 |
| July | 80° | 58° | 1.5 | 0.0 |
| August | 81° | 59° | 1.6 | 0.0 |
| September | 75° | 55° | 4.1 | 0.0 |
| October | 63° | 48° | 8.5 | 0.1 |
| November | 52° | 42° | 13.4 | 2.1 |
| December | 46° | 37° | 13.8 | 5.4 |
Station: Portland Kgw-Tv (NOAA NCEI USC00356749), about 1 km from central Portland. “Rain days” count days with 0.10" or more of precipitation.
The rules we check
- Cover tender plants when the overnight low is forecast at 34°F or colder.
- At 35–36°F, Fairsky still says cover when the night looks clear and calm (little cloud, wind 5 mph or less), because the ground can frost before the air hits 32°F. (Fairsky default: no source gave a number)
- 32°F or colder is a freeze.
- 28°F or colder is a hard freeze, which kills most tender vegetation; bring pots inside, since covers may not be enough.
Your product's label always wins. Labels differ by product; in the app you can enter your label's temperature range and rain-free hours, and the verdict uses them instead.
Sources: NWS glossary: frost advisory · NWS glossary: hard freeze
More home and yard jobs in Portland
- Stain a deckDeck and fence stain: 50–90°F, dry wood, 24 rain-free hours after.
- Paint a house exteriorExterior latex paint: 40°F and up, 5°F above the dew point, 4 dry hours after.
- Pour concreteConcrete: 40–85°F, no rain for 24 hours, no freezing for 48.
- Spray weedsWeed killer: 3–10 mph wind, 45–85°F, 4 rain-free hours after.
- Apply pre-emergentCrabgrass pre-emergent: before soil holds 55°F (about 200 GDD), then water it in.
- Plant grass seedCool-season grass seed: soil about 50–65°F, highs 60–80°F, no washout rain.
- Seal a drivewayAsphalt sealcoat: 55°F and rising, 50°F overnight, 36 rain-free hours.
The app covers 47 activities in all, from mowing to a round of golf: see every activity and its rules.
Cover plants for frost in nearby cities
- Seattle, WA145 miles away
- Spokane, WA290 miles away
- Boise, ID345 miles away
- Sacramento, CA483 miles away
- Stockton, CA527 miles away
- San Francisco, CA535 miles away
All cover plants for frost cities: Cover plants for frost, by city · Home and yard in Oregon
Questions
How is this verdict made?
We take the National Weather Service hourly forecast for Portland and check each hour against the thresholds listed above. The result is guidance, not a guarantee; your product's label always wins.
Will it frost tonight in Portland?
Frost is possible when the forecast low is in the mid-30s °F or colder, especially on clear, calm nights. The verdict above checks Portland's low tonight and this week.
Fairsky is not a substitute for official warnings. For warnings, go to weather.gov.
Live forecasts: National Weather Service / NOAA (public domain), fetched by your browser. Climate averages: NOAA NCEI U.S. Climate Normals, 1991–2020 (public domain). Activity thresholds: product data sheets, ACI and university extension guidance, linked on each page; your product’s label wins.