In 1989, the National Weather Service retired its Coastal Warning Display, which had been in use nation-wide for more than 100 years. The display stations were established at yacht clubs, marinas, and Coast Guard stations to hoist flags, pennants and colored lights to warn mariners of storms at sea. The display stations were individually notified by the National Weather Service to raise the signals and again to lower them when the hazards passed.
However, many coastal establishments continued to use the flags out of habit and tradition. In June, 2007, the U.S. Coast Guard re-established the Coastal Warning Display as an adjunct to frequently updated telephone recordings and NOAA Weather Radio. Certainly the flags are not a substitute for the superior electronic means of communication that are now available, but in coastal areas (and inland waterways), the red flags are a great visual warning system, and a prompt to seek out more information.
I personally have never seen the hurricane warning flags. By the time those two flags were flying on a pole, I had skedaddled 200 miles inland.