red alert

noun

: the final stage of alert in which enemy attack appears imminent

broadly : a state of alert brought on by impending danger

Synonyms of red alert

• watch
• watchfulness
• alert
• alertness
• vigilance

Examples of red alert in a Sentence

The troops have been put on red alert.

the paparazzi were on red alert for sightings of the hot new Hollywood couple

Recent Examples on the Web

France is under rare ‘red alert’ heat warnings, with temperatures over 100 degrees forcing restrictions on public drinking, canceled trains and concerts, and hundreds of schools closed amid safety fears. — Angela Charlton, Los Angeles Times, 21 June 2026

About a third of France is under the heat red alert Sunday, when temperatures are expected to reach 104 degrees Fahrenheit in some areas. — CBS News, 21 June 2026

About a third of France is under the national weather service’s heat red alert Sunday and temperatures are high nationwide, expected to reach 40 C (104 F) on Sunday in some areas, in a country where air-conditioning isn't widespread. — ABC News, 21 June 2026

The Associated Press reported that the Vatican was hit with a record-high heat wave this week, and the Rome municipality issued the year's first red alert, the highest level, for Thursday. — Charlotte Phillipp, PEOPLE, 28 May 2026

Word History

First Known Use

1941, in the meaning defined above