St. Louis, MO Climate Specs + Top-Rated Window Installers
St. Louis sits in IECC climate zone 4A, which sets the energy-performance bar here no matter who ends up installing your windows. A window license file doesn't cover St. Louis on this site, so Google Maps supplies the 9 ranked names you see below. Checked October 2026.
Google Maps ratings checked · How we rank
4AIECC climate zone · ENERGY STAR North-Central zone
St. Louis's climate zone, in plain terms
St. Louis, MO-IL runs a January average near 33°F and climbs to about 81°F by July, a swing that adds up to roughly 4,292 heating degree days most winters, with 1,769 on the summer cooling side of the ledger.
That load is the actual argument for paying up for a better U-factor in St. Louis, separate from anything a brochure claims.
Zone 4A's requirement is the floor; St. Louis's specific load is what tells you whether beating that floor is worth the extra cost.
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 1.5 mi away.
What FEMA's risk data says about St. Louis
St. Louis city's hail risk sits at Relatively Moderate and its wildfire risk at Very Low, according to FEMA's National Risk Index.
Hail risk matters for glass and screen durability in St. Louis; 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 St. Louis installer before you settle on a product line.
- Hurricane
- Very Low
- Strong wind
- Relatively High
- Winter weather
- Relatively Moderate
Data: FEMA, National Risk Index for Natural Hazards - County-level table, v1.20 (v1.20, December 2025).
Guides to finish before St. Louis 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.
St. Louis's top-rated window installers, by Google
The order below weighs a Google rating against its review count, the same way this site weighs a U-factor against a brochure claim: on the number, not the name. Treat it as a rating, never as proof of a license, bond or HVHZ approval.
- Chaney Windows And DoorsGoogle reviews
- STL Windows DirectGoogle reviews
- Glass Doctor of Greater St. LouisGoogle reviews
- Empire Supply CoGoogle reviews
- Missouri Glass CompanyGoogle reviews
- Gravois GlassGoogle reviews
- Viviano Windows & DoorGoogle reviews
- Winco Window CompanyGoogle reviews
- Penny WindowGoogle reviews