Updated: November 28, 2023
ʻUlupalakua Ranch on Maui had its lowest May rainfall total since 2012 according to the latest Monthly Precipitation Summary from the National Weather Service.
The report was compiled by Kevin R. Kodama, Senior Service Hydrologist with the NOAA/NWS Weather Forecast Office Honolulu.
While most of the state, including Molokaʻi and Lānaʻi, received near to above average rainfall for the month of May, the island of Maui was an outlier as most of its gauges posted below average monthly totals, according to Kodama.
The USGS’ gauge on Puʻu Kukui had the highest monthly total of 17.14 inches (62% of average), and the highest daily total of 5.43 inches on May 31. The Kamalō gauge on Molokaʻi had its highest May total on record.
Most of the gauges in Maui County had near to above average rainfall totals for 2023 through the end of May. The USGS’ rain gauge at West Wailuaiki Stream had the highest year-to-date total of 106.22 inches (99% of average).
Statewide, the 2023 Hawaiian Islands dry season had a late start due to generally wetter than average conditions during the month of May.
“The main reason for the enhanced rainfall was the presence of several low pressure systems aloft, especially during the first and last weeks of the month, that resulted in unstable conditions over the state,” according to the report.
There was one notable flash flood event during the month. On the morning of May 19, a low pressure system aloft helped trigger thunderstorms along the coastal sections of the North Kona and South Kohala Districts of the Big Island. Although brief, the passage of these thunderstorms with rainfall intensities reaching 2 to 3 inches per hour resulted in the flooding of roads in the Puakō region of the island. Heavy rainfall also occurred over portions of Kauaʻi (1 to 3 inches) and Oʻahu (1 to 2 inches), but did not cause significant flooding problems.
Additional incidents of heavy rainfall occurred on May 2 and May 30. The early May event was produced by a low pressure system west of the main Hawaiian Islands. The May 30 event occurred over the Big Island during the afternoon hours.
The rest of the month had mainly moderate to fresh trade wind conditions across the state, as would be expected for this time of the year, according to Kodama.
“Although May was wetter than average in many areas of the state, the forecast for the rest of the dry season called for below average rainfall and the onset of drought conditions over portions of the state during the summer,” according to the report.