One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's a good idea to estimate when it's the best time to plant onions by using the USDA zone info for Tomah.

Planting Calendar for Onions

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

Onions can survive in quite a bit of cold which means that you can plant them quite a bit earlier in the year than more sensitive plants.

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

The last month that you can plant onions and expect a good harvest is probably August. If you wait any later than that and your onions may not have a chance to grow to maturity. If you are starting your onions indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Tomah the average date of last frost happens on May 15. You can expect an average low temperature of -25°F in the coldest months of winter.

Keep in mind that USDA zone info for Tomah is just an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Tomah there is a last frost after May 15 so always be ready to protect your onions in the event of one of those late frosts.

USDA Zone Info for Tomah

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Tomah

You may be interested in your other planting guides for Tomah.