Record Rainfall Conditions Reported on Big Island for Month of June
The unusual June rainfall conditions for the Big Island resulted in the highest and lowest monthly rainfall records broken in the same month.
On the high side, the Kealakekua rain gage posted its highest June rainfall total of 10.11 inches in a data record going back to 1991, according to the National Weather Service monthly rain summary report. In contrast, Upolu Airport, on the north tip of the Big Island, reported its lowest June rainfall total of .37 inches.
The data record for the Upolu Airport site also goes back to 1991.
While drought conditions intensified across the Hawaiian Islands throughout the month of June, the main exceptions were along the slopes of the Kohala Mountains and in the Pōhakuloa region of the Big Island, according to the report. The Pi‘ihonua gage had the highest year-to-date total of 107.23 inches (120% of average).
Overall, rainfall totals for 2021 through the end of June were near to above average at most of the Big Island gages. Although the trade winds persisted throughout the month of June, the rain summary indicated, most of the highest rainfall totals came from the leeward side of the island instead of the windward side resulting in rainfall totals along the Kona slopes region higher than average for the second consecutive month.
Many of the totals from the windward districts of South Hilo and Puna were in the range of 2 to 6 inches. Several totals from the Kona slopes region were from 6 inches to more than 10 inches. Among the automated rain gages, the USGS’ rain gage at Kawainui Stream had the highest monthly total of 11.02 inches (112% of average).
However, a manually read CoCoRaHS volunteer network gage at Holualoa in the North Kona District had a higher June total of 11.22 inches, including the highest daily total of 3.73 inches logged on the morning of June 20. Most of this rainfall likely occurred on the afternoon and evening of June 19.
The late afternoon and early evening of June 19 produced heavy showers along the Kona slopes. On June 26, there were heavy showers on the leeward Kohala slopes.
According to the report, both events produced minor flooding, with the June 19 event resulting in the brief partial closure Queen Ka‘ahumanu Highway due to debris on the road.