USDA Plant Hardiness Zones for Wisconsin

USDA Hardiness Zones and Average Annual Minimum Temperatures
Zone	Average Annual Minimum Temperature	Representative Woody Plants
3a	-35° to -40° F	Aronia melanocarpa (Black chokeberry) Cornus alternifolia (Pagoda dogwood) Juniperus communis (Common juniper) Malus baccata (Siberian crabapple) Spirea alba (Meadowsweet) Spirea tomentosa (Hardhack) Thuja occidentalis (American arborvitae) Viburnum lentago (Nannyberry)
3b	-30° to -35°F
4a	-25° to -30° F	Acer saccharum (Sugar maple) Hydrangea paniculata (Panicle hydrangea) Juniperus chinensis (Chinese juniper) Ligustrum amurense (Amur River privet) Parthenocissus quinquefolia (Virginia creeper) Spiraea x vanhouttei (Vanhoutte spirea)
4b	-20° to -25° F
5a	-15° to -20° F	Cornus florida (Flowering dogwood) Deutzia gracilis (Slender deutzia) Parthenocissus tricuspidata (Boston ivy) Taxus cuspidata (Japanese yew)
5b	-10° to -15° F

Temperatures listed are the average yearly minimum temperatures, not the coldest temperatures ever recorded. A plant not fully dormant can be damaged at much warmer temperatures. Other factors, including soil conditions, chilling requirements and growing degree days, are critical to plant performance within a climate zone.