September broke more rainfall records, according to the latest monthly report from the Hawaiʻi Climate Data Portal. So far, 2026 is on track to become one of Hawaiʻi’s wettest years in the last century.
Kauaʻi had its wettest September on record, receiving more than a foot of rain above its typical monthly average.
Much of that rainfall occurred during Hurricane Lowell, which drenched the Garden Isle early in the month. Kauaʻi’s North Shore got 17 inches of rain from Lowell, and the summit of Mount Waiʻaleʻale recorded a staggering 36 inches over three days. Hurricane Nolo then brought even more rain.
Across the archipelago, Hawaiʻi Island felt the heat, logging its warmest September on record. Temperatures were 2.6°F above normal.
While rainfall and heat trends were most pronounced on Kauaʻi and Hawaiʻi Island, “nearly the entire state was significantly warmer and wetter this last month,” HCDP Director Ryan Longman told HPR.
Hawaiʻi still has two months left in an unprecedented hurricane season, which officially ends on Nov. 30.
El Niño is a significant factor in why Hawaiʻi is experiencing “record-breaking rain and record heat at the same time,” according to Longman.
During El Niño, sea surface temperatures heat up in the Central Pacific Ocean.
“That heat acts like a high-octane fuel, helping tropical storms form closer to Hawaiʻi, grow stronger, and dump massive amounts of rain on the islands,” Longman said.
And that warmer water also traps heat around the islands, preventing air temperatures from cooling down and driving up humidity.
Find HCDP’s latest climate summary here.
HCDP is a collaborative effort based at the University of Hawai’i Sea Grant College Program, which is an underwriter of HPR.
