Palo Alto, CA: Climate Zone, Risk and Window Requirements
Local risk and climate data for Palo Alto, CA are below, translated into plain terms for a window buyer rather than left as raw codes. Use it to check a proposed spec before you sign, not just to browse.
Licenses checked · California Contractors State License Board
3CIECC climate zone · ENERGY STAR South-Central zone
What zone 3C means for a Palo Alto window
Palo Alto falls in IECC climate zone 3C, and ENERGY STAR separately groups Santa Clara County into its South-Central zone for window certification.
Those two numbers, not the brand on the box, set the U-factor and SHGC worth checking on any quote you get in Palo Alto.
A San Jose-Sunnyvale-Santa Clara, CA contractor who can't name either one on request is worth a second question before you sign.
Data: U.S. EPA / DOE, ENERGY STAR, ENERGY STAR Version 7.0 Climate Zones by County/ZIP (Windows, Doors, and Skylights) (V7.0); Pacific Northwest National Laboratory (DOE Building America), Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (PNNL-33270) (2021 IECC), from the nearest NOAA station 3.3 mi away.
Storm and weather risk around Palo Alto
Santa Clara County's hail risk sits at Relatively Low and its wildfire risk at Relatively Moderate, according to FEMA's National Risk Index.
Hail risk matters for glass and screen durability in Palo Alto; wildfire risk matters more for the frame material and nearby vegetation than for the glass itself.
Either way, it's a reasonable question to bring to a Palo Alto installer before you settle on a product line.
- Strong wind
- Very Low
- Winter weather
- Very Low
Data: FEMA, National Risk Index for Natural Hazards - County-level table, v1.20 (v1.20, December 2025).
Guides to finish before Palo Alto window bids come in
- How to Read an NFRC Window Label Four numbers on one sticker decide most of a window's real-world performance. Here's what each one means.
- ENERGY STAR Window Criteria by Climate Zone ENERGY STAR splits the country into four zones, each with its own numbers. Here they are, and why the Northern zone works backward from the other three.
- Impact Windows vs. Shutters in Florida's Hurricane Zones Florida gives homeowners two paths to a protected opening. Here's how each one is tested, and where the HVHZ raises the bar further.
Window installers with the longest license records in Palo Alto
Oldest license first, newest last, pulled directly from the state's file. This list isn't for sale.
- Palo Alto Glass INCVerify license
- Bella's GlassVerify license
- The Bay Shower DoorsVerify license