Idaho's USDA hardiness zone will vary greatly, depending on where you live. For the Boise, Idaho area, where we are located, our USDA hardiness is 6b. That's from -5 degrees below zero to 0 degrees. Some feel we belong in zone 7 while others feel USDA hardiness should be zone 5. In part, the particular part of town you live in may make a difference on your hardiness zone. Add to that, some gardening folks have great protection from the elements while others have little protection.
USDA HARDINESS ZONE
Fahrenheit
Zone 1 Below -50 Zone 6 -10 to -0
Zone 2 -50 to -40 Zone 7 0 to 10
Zone 3 -40 to -30 Zone 8 10 to 20
Zone 4 -30 to -20 Zone 9 20 to 20
Zone 5 -20 to -10 Zone 10 30 to 40