Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By looking at the USDA zone info for North Chicago you will be able to estimate when to plant onions.

Planting Calendar for Onions

Frost tolerance for onions:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Since onions are one of those plants that can tolerate quite a bit of cold weather you can plant them quite a bit earlier in the year than other frost tender plants.

The earliest that you can plant onions in North Chicago is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant onions and expect a good harvest is probably September. Any later than that and your onions may not have a chance to grow to maturity. Starting your onions indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost has passed is on April 15 in North Chicago. You can expect an average low temperature of -15°F in the coldest months of winter.

Keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for North Chicago and it will vary from year to year. Half of the time in North Chicago it frosts late in the year after April 15 so just be sure to be ready to protect your onions in the event of a surprise late frost.

USDA Zone Info for North Chicago

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in North Chicago

You may be interested in your other planting guides for North Chicago.