Last frost date in Ottawa, Illinois
April 27
Average last frost in spring. In an early year (1 in 10) it's over by April 12; in a late year (1 in 10) it comes after May 13.
October 17
Average first frost in fall. 1 year in 10 it comes by October 3.
Source: NOAA U.S. Climate Normals 1991–2020, station Marseilles Lock (USC00115372), 4 miles from Ottawa, elevation 490 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 12 | Apr 27 | May 13 |
| First frost in fall | Oct 3 | Oct 17 | Oct 29 |
An early or late year is one in 10: 1 year in 10 the frost comes before the early date, and 1 year in 10 after the late date.
Frost-free days in an average year: 171
Planting calendar for Ottawa
Fall planting
USDA dates for places whose average first freeze is about October 20 (Ottawa: October 17).
- Black-eyed peasJune 1 – July 1 (past for this year)
- Celery and celeriac plantsJune 1 – Aug 1 (past for this year)
- CucumbersJune 1 – July 15 (past for this year)
- Eggplant plantsJune 1 – July 1 (past for this year)
- New Zealand spinachJune 1 – Aug 1 (past for this year)
- OkraJune 1 – Aug 1 (past for this year)
- Peppers plantsJune 1 – July 10 (past for this year)
- SalsifyJune 1 – July 1 (past for this year)
- SoybeansJune 1 – July 5 (past for this year)
- Summer squashJune 1 – July 20 (past for this year)
- Sweet cornJune 1 – July 20 (past for this year)
- Sweet potatoesJune 1 – 15 (past for this year)
- Swiss chardJune 1 – Aug 1 (past for this year)
- TomatoesJune 1 – July 1 (past for this year)
- Winter squashJune 1 – July 1 (past for this year)
- Cantaloupe (muskmelon)June 15 – July 20 (past for this year)
- CarrotsJune 15 – Aug 1 (past for this year)
- Florence fennelJune 15 – Aug 1 (past for this year)
- Lima beansJune 15 – 30 (past for this year)
- PotatoesJune 15 – July 15 (past for this year)
- WatermelonJune 15 – July 20 (past for this year)
- Witloof chicoryJune 15 – July 15 (past for this year)
- BeetsJuly 1 – Aug 5 (past for this year)
- Broccoli plantsJuly 1 – Aug 1 (past for this year)
- Brussels sprouts plantsJuly 1 – Aug 1 (past for this year)
- Cabbage plantsJuly 1 – 20 (past for this year)
- Cauliflower plantsJuly 1 – Aug 5 (past for this year)
- Snap beansJuly 1 – Aug 1 (past for this year)
- RutabagaJuly 10 – 20 (past for this year)
- Chinese cabbageJuly 15 – Aug 15 (past for this year)
- Collards plantsJuly 15 – Aug 15 (past for this year)
- EndiveJuly 15 – Sept 1 (past for this year)
- KaleJuly 15 – Aug 15 (past for this year)
- KohlrabiJuly 15 – Aug 15 (past for this year)
- Leaf lettuceJuly 15 – Sept 1 (past for this year)
- ParsleyJuly 15 – Aug 15 (past for this year)
- SorrelJuly 15 – Aug 15 (past for this year)
- TurnipsJuly 15 – Aug 15 (past for this year)
- DandelionAug 1 – Sept 15 (past for this year)
- Head lettuce plantsAug 1 – 30 (past for this year)
- Mustard greensAug 1 – Sept 1 (past for this year)
- RadishesAug 1 – Oct 1 (past for this year)
- SpinachAug 20 – Sept 10 (past for this year)
- Corn saladSept 1 – Oct 15 (past for this year)
- Upland cressSept 1 – Oct 15 (past for this year)
- Rhubarb plantsOct 15 – Dec 1Now
- Asparagus plantsNov 1 – Dec 15Soon
USDA lists chervil and chives, garlic, horseradish, leeks, onion plants, onion seed, onion sets, parsnips, garden peas, shallots as generally spring-planted here.
Spring planting
USDA dates for places whose average last freeze is about April 30 (Ottawa: April 27).
- Corn saladMar 1 – May 1
- Onion setsMar 10 – Apr 10
- Cabbage plantsMar 15 – Apr 10
- GarlicMar 15 – Apr 15
- Onion seedMar 15 – Apr 15
- Asparagus plantsMar 20 – Apr 15
- Chervil and chivesMar 20 – Apr 20
- DandelionMar 20 – Apr 20
- Garden peasMar 20 – May 1
- PotatoesMar 20 – May 10
- RadishesMar 20 – May 10
- Rhubarb plantsMar 20 – Apr 15
- SpinachMar 20 – Apr 20
- TurnipsMar 20 – May 1
- BeetsApr 1 – June 15
- Broccoli plantsApr 1 – May 1
- Brussels sprouts plantsApr 1 – May 1
- Collards plantsApr 1 – June 1
- EndiveApr 1 – May 1
- Florence fennelApr 1 – May 1
- Head lettuce plantsApr 1 – May 1
- Horseradish plantsApr 1 – 30
- KaleApr 1 – 20
- KohlrabiApr 1 – May 10
- Leaf lettuceApr 1 – June 1
- LeeksApr 1 – May 1
- Mustard greensApr 1 – May 10
- Onion plants plantsApr 1 – May 1
- ParsleyApr 1 – May 1
- ParsnipsApr 1 – May 1
- SalsifyApr 1 – May 15
- ShallotsApr 1 – May 1
- SorrelApr 1 – May 15
- CarrotsApr 10 – June 1
- Cauliflower plantsApr 10 – May 10
- Upland cressApr 10 – May 10
- Celery and celeriac plantsApr 15 – May 1
- Swiss chardApr 15 – June 15
- New Zealand spinachMay 1 – June 15
- RutabagaMay 1 – June 1
- Summer squashMay 1 – 30
- OkraMay 10 – June 1
- Snap beansMay 10 – June 30
- Sweet cornMay 10 – June 15
- TomatoesMay 10 – June 15
- Black-eyed peasMay 15 – June 1
- Cantaloupe (muskmelon)May 15 – June 15
- CucumbersMay 15 – June 15
- Eggplant plantsMay 15 – June 10
- Lima beansMay 15 – June 15
- Peppers plantsMay 15 – June 10
- SoybeansMay 15 – June 15
- WatermelonMay 15 – June 15
- Sweet potatoesMay 20 – June 10
- Witloof chicoryJune 15 – July 1
USDA lists chinese cabbage as generally fall-planted here.
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5 (earliest safe spring and latest safe fall dates), applied to this place's NOAA frost dates. “Plants” means setting out transplants, not sowing seed. How we match the table.