yellow alert

noun

1. (in military or civilian defense) the first alert given when enemy aircraft are discovered approaching a military installation, city, coastline, etc. Compare blue alert, red alert, white alert.
2. the signal or alarm sounded for this alert.
3. any primary stage of alert, as when toxic chemicals have escaped in a particular area and a potential hazard exists.

Word History and Origins

Origin of yellow alert¹

First recorded in 1965–70

Example Sentences

Calmac said the Ardmhor to Eriskay route is on yellow alert and liable to cancellation or disruption.

From BBC

A yellow alert - the second of the four weather tiers - is in place in the capital, with an orange alert in Bordeaux and Lyon.

From BBC

It has now issued a yellow alert for England for a further week, warning of an increased use of health care services by vulnerable populations and an increase in risk to health for people aged 65 years and over, those with pre-existing health conditions, and some other vulnerable groups, such as those sleeping rough.

From BBC

A yellow alert is in place from 18:00 in the Highlands, Perth and Kinross, Stirling and Argyll and Bute.

From BBC

Italy’s civil protection agency has maintained a yellow alert on the site, denoting caution but not imminent danger.

From Washington Times