Frost dates for Ottawa, IL
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 27
typical year
Safe to plant
May 13
frost is over in 9 of 10 years
First fall frost
October 17
typical year
Growing season
171 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 30 – Apr 13 | – |
| Spinach | – | Mar 16 – Apr 6 | Aug 22 – Sep 5 |
| Lettuce | – | Mar 30 – Apr 20 | Aug 22 – Sep 5 |
| Radishes | – | Mar 30 – May 11 | Sep 5 – 19 |
| Onions | – | Mar 30 – Apr 13 | – |
| Potatoes | – | Apr 6 – 20 | – |
| Carrots | – | Apr 6 – 27 | Jul 25 – Aug 8 |
| Beets | – | Mar 30 – Apr 13 | Aug 8 – 22 |
| Kale | Feb 16 – Mar 2 | Mar 30 – Apr 13 | Aug 8 – 22 |
| Broccoli | Feb 16 – Mar 2 | Apr 13 – 27 | Aug 8 – 22 |
| Cabbage | Feb 2 – 16 | Mar 30 – Apr 13 | Aug 8 – 22 |
| Garlic | – | – | Sep 5 – 26 |
| Warm-season crops | |||
| Tomatoes | Mar 18 – Apr 1 | May 13 – 27 | – |
| Peppers | Mar 11 – 25 | May 20 – Jun 3 | – |
| Cucumbers | – | May 13 – Jun 3 | – |
| Zucchini | – | May 13 – Jun 10 | – |
| Pumpkins | – | May 13 – Jun 3 | – |
| Green beans | – | May 13 – Aug 8 | – |
| Sweet corn | – | May 13 – Jun 10 | – |
| Basil | Apr 8 – 22 | May 20 – 27 | – |
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 13 | April 27 | April 12 |
| Fall frost before | October 3 | October 17 | 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 15 (May 1 in a late year), and the first one in fall around October 27.
Towns that use these dates
This is the nearest NOAA station with frost records for 5 towns.
Ottawa, Marseilles, Seneca, Sheridan, Grand Ridge
Where these dates come from
NOAA weather station MARSEILLES LOCK, IL US (USC00115372), 1991–2020 climate normals. It's the nearest station for 6 zip codes, all within 14 miles:
60549, 60551, 60557, 61325, 61341, 61360
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.