What plant hardiness zone is Alto Pass

Alto Pass is located at Union County, Illinois (IL), USA.

Plant hardiness zone (winter frost zone or gardening zone) for Alto Pass is 6b by the USDA scale.

Coldest zone's winter temperature is −5 … 0 °F.

Plants of 6b USDA hardiness zone suitable for outdoor gardening and growing in this winter frost zone 6b USDA.

Alto Pass, Illinois @ wikipedia.