The big wind, or “;dust devil,”; that blew a portion of a roof off a school building on the Big Island is rare in Hawaii, according to the National Weather Service.

“;A dust devil — especially one that produces wind damage — is very rare,”; National Weather Service forecaster Derek Wroe said yesterday.

Wroe said the duration of strong winds for the past five days is unusual.

He said the gusts are expected to continue through tomorrow and begin subsiding Thursday and Friday.

Wroe said tradewinds from the northeast can be strong near the end of winter and the start of spring, although these type of winds can happen at any time of the year.

Work was continuing to repair the roof of the building housing the administrative offices and three classrooms at Kau High School and Pahala Elementary.

The wind caused “;severe damage,”; tearing off a portion of the roof above the registrar's office and two classrooms at about 11:30 a.m. Saturday.

Fire officials said a section of the roof about 80 feet long and 30 to 40 feet wide blew off in a severe wind event.

No one was injured and students were in school yesterday.

“;The school is opened, and accommodations are being made for the classrooms that were impacted,”; said school Principal Sharon Beck.

Beck said safety was a major priority.

“;All safety measures are in place,”; she said.

Wroe said a weather advisory for the Kau District has been in effect since last week, warning of the potential for 30 mph winds, gusting up to 50 mph.

He said the weather service was unable to confirm the nature of the wind, but based on some eyewitness reports, it seemed like a dust devil.

Typically short-lived and about a couple of hundred feet wide at the most, dust devils are formed when high winds strike terrain and turn in a circular motion, he said.

Wroe said that within a dust devil, the winds could gain more speed.

He said tornadoes, which are wider and typically faster, are formed through thunderstorms.

Wroe said within the last five days, the weather service had two reports of smaller dust devils occurring on Oahu and Kawaihae in West Hawaii.

He said he did not know where the dust devil occurred on Oahu.

Beck said she wanted to thank the workers and volunteers who helped during the weekend.