Rainy Weather to Continue Through Midweek

Rainy weather continues on the Big Island, apparent by heavy downpours, thunderstorms and the issuing of flood advisories the afternoon of Monday, May 2. But according to a hydrologist with the National Weather Service in Honolulu, the wet weather hasn’t been anything out of the ordinary.

According to data from the NWS, as of 2:45 a.m. Monday, the latest available from the weather service, the Hilo area had received 1.08 inches of rain so far for May, 0.82 of an inch more than the normal amount. Thunderstorms and heavy rain moved in throughout the day, causing the NWS to issue flood advisories for both sides of the island at certain points.

The total amount of rainfall the Hilo area saw in April was just less than 16 inches, at 15.67 inches, according to NWS data. The average amount of rain for during the month of April is 9.4 inches, so the Hilo area received 6.27 inches more rainfall throughout the month than normal. That’s also nearly 8 inches more than 2021, when the Hilo area received 7.8 inches of rain in April.

The greatest amount of rainfall in a 24-hour period during the month was 5.02 inches recorded April 15-16.

“While it has been wetter than normal recently, it isn’t close to being unprecedented,” Kevin Kodama, senior service hydrologist with the National Weather Service in Honolulu, told Big Island Now in an email Monday, May 2. “I think if you ask the old-timers who know Hilo rain, me included, it isn’t that unusual.”

Kodama said stronger than normal trade winds coupled with low pressure systems aloft have provided some unstable conditions, and the recent rainfall is in line with normal variability. The nearly 16 inches of rain recorded at the Hilo airport in April makes this the 15th highest April rainfall total since 1950, but well off the record of 43.24 inches in 1986.

Not even the recent winter weather at Big Island summits is all that unusual for it being the beginning of May.

“It is not common to have snow on the summits in April, but not unheard of,” Kodama said. “In fact, we’ve had snow at the summits in June. Again, not common, but it happens.”

As far as West Hawai‘i goes, Kodama said much of the Kona slopes got near to above average rainfall in April.

And it looks like the wet weather will continue for at least a little longer.

“We’re expecting it to continue being rather rainy through midweek,” Kodama said. “By late this week, we should see less rain on the Big Island.”

Despite the rainy weather as of late, NWS data also show that the Hilo area is still more than an inch away from the normal amount of rainfall it receives from March 1-May 1 and more than 11 inches behind the normal rainfall amount for Jan. 1-May 1.

So has all of the recent rain helped in areas of the island experiencing drought, such as portions of South and North Kohala and Hāmākua?

“Because the trades have been persistent, not much is getting to the South Kohala District or the leeward portions of the Hāmākua and North Kohala districts,” Kodama said. “These areas are seeing enough rain to prevent conditions from worsening, but not enough to pull the area out of drought. The strong winds have not helped either, since the moisture evaporates quickly.”

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