First and last frost dates in Silverton, OR
At the selected station, the median last spring freeze is March 28. The median first fall freeze is November 10. Compare the 10%, 30% and 50% historical freeze probabilities below.
Spring and fall freeze dates
32°F / 0°CA 30% risk date leaves a smaller historical chance of a later spring freeze than the median. It is not a forecast or a guarantee.
Plan planting dates in Silverton
Select a freeze probability
The 10% date is a more cautious spring starting point. Tender crops may need warmer soil and nights too.
Calculate when to start seeds
Use the number of weeks on your seed packet to work backwards from a suitable outdoor date.
Check the local forecast
A normal describes the past. Check this year’s forecast before moving plants outdoors.
Indoor seed-starting dates by crop
Work backwards from an outdoor target of Apr 11: the selected spring freeze date plus an editable seven-day delay.
These are transplant-growing windows, not a recommendation to plant every crop on the same day. Adjust the outdoor target for your crop, soil temperature and local conditions.
| Crop | Time indoors | Illustrative sowing window | Your plan |
|---|---|---|---|
| Tomatoes | 5–6 weeks | Feb 28 – Mar 7 | Plan tomatoes → |
| Peppers | 8–10 weeks | Jan 31 – Feb 14 | Plan peppers → |
| Eggplant | 8–10 weeks | Jan 31 – Feb 14 | Plan eggplant → |
| Broccoli | 4–6 weeks | Feb 28 – Mar 14 | Plan broccoli → |
| Lettuce | 2–4 weeks | Mar 14 – Mar 28 | Plan lettuce → |
| Cucumbers | 3–5 weeks | Mar 7 – Mar 21 | Plan cucumbers → |
Indoor durations: University of Maryland Extension. The seven-day delay is our example, not the university’s prescription. Your seed packet takes priority.
Calculate fall planting dates
Compare your seed packet’s days to maturity with the time before your selected fall freeze date.
Freeze dates by probability
Download these dates| Historical probability | Last spring freeze on or after | First fall freeze on or before | Interval |
|---|---|---|---|
| 50% — median | March 28 | November 10 | 227 days |
| 30% — lower risk | April 4 | November 2 | 212 days |
| 10% — more cautious | April 19 | October 25 | 189 days |
“Frost date” is common gardening shorthand. These NOAA figures describe air temperatures reaching 32°F; frost on leaves can occur under different conditions. The two tail probabilities do not give the probability of a completely freeze-free season.
Frost date questions
How we use the dataWhen is the last frost in Silverton?
The median last 32°F spring freeze at the selected station is March 28. The more cautious 10% date is April 19. Neither date predicts the weather in a particular year.
Can I plant tomatoes on the last frost date?
Use the date as one input. Tomatoes need warm soil, suitable nighttime temperatures, and hardening off. A 50% historical date still carries substantial freeze risk. Check your seed instructions, local extension guidance and current forecast.
Why do other websites show a different date?
Sites may use another station, reference period, temperature threshold or probability. This guide identifies the station and shows three probabilities so you can compare like with like.