California's rule is a single hard line rather than graduated guidance. At or above one reading, CIF member schools must stop outdoor practice and competition; below it the bylaw says nothing at all.
AQI 151+
The bylaw's operative sentence, in full: "All CIF member schools must refrain from outdoor practice and/or competition when the Air Quality Index is 151 or higher."
The same bylaw names its acceptable sources: "Schools may use readings for their local area obtained through www.airnow.gov or a measurement device located outdoors on their physical campus."
That sentence is why this site's air gate reads AirNow: the bylaw names it as an acceptable source. It still does not make a website the decision-maker — your designated monitor is.
The bylaw is silent below that reading. Your section, district or local health department may set something stricter, and the heat gate is unaffected either way.
On a clear day, pick landmarks about 1, 3 and 5 miles from the field. Stand with the sun behind you: when a landmark's outline can no longer be seen, visibility is shorter than that distance.
In smoke or haze, check the AQI or the visibility index at least hourly during practices and games — conditions turn over fast.
Every threshold and quotation on this page was read off the primary document. CIF Bylaw 503.K(2) Air Quality Index Protocol (Approved January 2019 Federated Council), as printed in the CIF North Coast Section 2026-2027 Constitution & General Bylaws, p.105
Cross-checked against the primary document on 2026-08-09
wbgtcheck.com is an independent tool. It is not affiliated with, endorsed by, or connected to the UIL, GHSA, NFHS, NATA, or any state athletic association.
Readings come from the EPA AirNow program, which republishes hourly observations from state, local and tribal air agencies. Credit belongs to those agencies first. Category colors follow the RGB values EPA specifies for the AQI, unaltered.
Using an online satellite map, locate three landmarks that can be seen from a specific venue. The landmarks you choose should be 1 mile away, 3 miles away and 5 miles away. […] Standing with the sun behind you, look at the three objects and when the outline of the landmark can no longer be seen, then the visibility range is less than the distance marker.