US Climate Zones (ASHRAE 169)

The IECC (International Energy Conservation Code) divides the U.S. into 8 climate zones, based on temperature, humidity, and rainfall, ranging from hot-humid (Zone 1) to subarctic (Zone 8).

Zone 1A

Hot-Humid – Very warm and moist (e.g., Miami, FL).

Zone 1B

Hot-Dry – Hot, arid regions (e.g., Phoenix, AZ).

Zone 2A

Warm-Humid – Warm with high humidity (e.g., Houston, TX).

Zone 2B:

Warm-Dry – Warm and dry climate (e.g., El Paso, TX).

Zone 3A

Hot-Humid – Less intense than Zone 1A (e.g., Atlanta, GA).

Zone 3B

Hot-Dry – Hot, drier areas (e.g., southern California).

Zone 3C

Coastal Marine – Moderate temps, moist air (e.g., San Francisco, CA).

Zone 4A

Mixed-Humid – Distinct seasons, humid (e.g., Washington, DC).

Zone 4B:

Mixed-Dry – Seasonal with dry air (e.g., Albuquerque, NM).

Zone 4C:

Marine – Cool summers, mild winters (e.g., Portland, OR).

Zone 5A

Cool-Humid – Cold winters, humid summers (e.g., Chicago, IL).

Zone 5B

Cool-Dry – Similar to 5A but drier (e.g., Denver, CO).

Zone 5C

Marine – Coastal, cool (e.g., Seattle, WA).

Zone 6

Cold-Humid – Colder winters, humid (e.g., Minneapolis, MN).

Zone 6B

Cold-Dry – Colder and drier (e.g., Helena, MT).

Zone 7

Very Cold – Long, harsh winters (e.g., Duluth, MN).

Zone 8

Subarctic/Arctic – Extremely cold (e.g., Fairbanks, AK).