red flag warning
Definition
A high-level alert issued by the National Weather Service in the United States when weather conditions—typically very low relative humidity, strong winds, warm temperatures, and dry fuels—create a high risk of rapid wildfire ignition and spread.
Informally, an obvious signal or indicator of impending danger or trouble, akin to waving a literal red flag.
Examples
Ignoring the red flag warning, Dave fired up the grill anyway, turning his cookout into a neighborhood legend—for all the wrong reasons.
The red flag warning had campers scrambling to douse their fires quicker than a kid caught sneaking cookies.
Under a red flag warning, even the local squirrels seemed to stash their nuts indoors, playing it safer than the humans.
She checked the app, saw the red flag warning, and swapped her beach bonfire plans for a cozy microwave s'mores session.