Unusually warm temperatures hitting Hawaii in recent weeks appear to be causing coral bleaching across the island chain at levels that local researchers say they’ve never seen before, with the worst damage emerging in the shallows along Oahu’s windward coast.

Seventy-five percent of the coral surveyed in the past week in Kaneohe Bay has shown recent signs of bleaching — anywhere from an early "paling" of their color to "100 percent white" indicating they’re either about to die or already dead, officials with the state’s Division of Aquatic Resources said Monday.

The surveys led by state agencies and university researchers follow recent reports of widespread coral bleaching. What they’ve found is "unprecedented for everyone who’s studied this in the past," said Zac Forsman, a coral recovery specialist with DAR.

The same bleaching problem is being reported at popular visitor sites such as Hanauma Bay and Waikiki — as well as on Maui, Hawaii island and the Northwestern Hawaiian Islands, said Frazer McGilvray, the division’s administrator.

The doldrum-like weather that has lingered across Hawaii in the past several weeks, with its hot air and low winds, has kept surface the sea temperatures close to shore far warmer than they typically are this time of year. It’s the second-hottest air temperature on record for September since the 1940s, McGilvray said.

Weather models from National Oceanic and Atmospheric Administration show that conditions leading to the bleaching will persist through the next four to six weeks, added Anne Rosinski, also of the Division of Aquatic Resources.