The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In San Diego you can estimate when it's the best time to plant onions by referring to the USDA zone info.

Planting Calendar for Onions

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

Onions are very cold tolerant which tells us that you can get them planted much earlier than more sensitive plants.

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

The last month that you can plant onions and expect a good harvest is probably October. If you wait any later than that and your onions may not have a chance to fully mature. If you are starting your onions indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In San Diego the average date of last frost happens on January 31. You should expect an average low temperature of 35°F in the coldest months of winter.

Always keep in mind that USDA zone info for San Diego 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 San Diego it frosts late in the year after January 31 so just be sure to be ready to cover your onions in the event of a surprise late frost.

USDA Zone Info for San Diego

Here is the info for USDA Zone 10b.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	35°F
Highest Expected Low	40°F

This means that on a really cold year, the coldest it will get is 35°F. On most years you should be prepared to experience lows near 40°F.

Plants to Grow in San Diego

You may be interested in your other planting guides for San Diego.