Rainfall Sets Record in Hilo Thursday

The heavy rainfall that prompted the issuing of a flood advisory Thursday set a record at Hilo International Airport.

The 3.70 inches of rain that fell was the highest amount ever recorded there for May 1, the National Weather Service said.

Nearly half of that – 1.78 inches – fell between 2 a.m. and 8 a.m., according to preliminary weather service data.

The old record for May was 2.11 inches, set in 1970.

The record for a calendar day in May is 7.89 inches, set on May 15, 1967. Strangely enough, the May record was tied on that same date in 1996.

Average rainfall at the airport in May is 8.12 inches, making it one of the drier months of the year.

The average annual precipitation at that gauge in Hilo — the nation’s rainiest city — is 126.72 inches.

Upslope areas of Hilo receive considerably more, as Piihonua averages 185.75 inches annually and Waiakea Uka 196.20 inches.

The rainiest inhabited place on the Big Island — as in where gauges are located — is Glenwood in upper Puna, where 233.53 inches falls in a “normal” year.

However, there are places on the slopes of Mauna Kea above Hilo where the average reportedly exceeds 250 inches annually.

The wettest spot in the state is Mount Waialeale on Kauai, which averages 393.85 inches each year.