According to the 2023 USDA Hardiness Zone Map Portland, Colorado is in Zones 5b (-15°F to -10°F), 6a (-10°F to -5°F) and 6b (-5°F to 0°F). This is a change from the 2012 USDA Hardiness Zone Map which has Portland in Zones 5a (-20°F to -15°F), 5b (-15°F to -10°F) and 6a (-10°F to -5°F).