Frost dates for Ontario, OR
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
April 21
typical year
Safe to plant
May 8
frost is over in 9 of 10 years
First fall frost
October 14
typical year
Growing season
176 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | Mar 24 – Apr 7 | – |
| Spinach | – | Mar 10 – 31 | Aug 19 – Sep 2 |
| Lettuce | – | Mar 24 – Apr 14 | Aug 19 – Sep 2 |
| Radishes | – | Mar 24 – May 5 | Sep 2 – 16 |
| Onions | – | Mar 24 – Apr 7 | – |
| Potatoes | – | Mar 31 – Apr 14 | – |
| Carrots | – | Mar 31 – Apr 21 | Jul 22 – Aug 5 |
| Beets | – | Mar 24 – Apr 7 | Aug 5 – 19 |
| Kale | Feb 10 – 24 | Mar 24 – Apr 7 | Aug 5 – 19 |
| Broccoli | Feb 10 – 24 | Apr 7 – 21 | Aug 5 – 19 |
| Cabbage | Jan 27 – Feb 10 | Mar 24 – Apr 7 | Aug 5 – 19 |
| Garlic | – | – | Sep 2 – 23 |
| Warm-season crops | |||
| Tomatoes | Mar 13 – 27 | May 8 – 22 | – |
| Peppers | Mar 6 – 20 | May 15 – 29 | – |
| Cucumbers | – | May 8 – 29 | – |
| Zucchini | – | May 8 – Jun 5 | – |
| Pumpkins | – | May 8 – 29 | – |
| Green beans | – | May 8 – Aug 5 | – |
| Sweet corn | – | May 8 – Jun 5 | – |
| Basil | Apr 3 – 17 | May 15 – 22 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | May 8 | April 21 | April 4 |
| Fall frost before | September 29 | October 14 | October 29 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around April 2 (April 23 in a late year), and the first one in fall around October 27.
Where these dates come from
NOAA weather station ONTARIO MUNI AP, OR US (USW00024162), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 7 miles:
97914
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.