August 2026 Monthly Rainfall Summary for Hawaii

Monthly Precipitation Summary 

State of Hawaii 

Month: August 2026

Prepared: September 9, 2026

Note: This summary uses the arithmetic mean, or average, for “normal” rainfall values.

Averages used in this summary have switched to the 1991-2020 values where available.

Headline: Hurricane Lala dominated the rainfall in August, providing many locations with nearly their entire month’s total in just a day or two. 

State: [Text data table for rain gages]

August began with breezy trade winds that weakened to light to moderate speeds through the 5th as the remnants of Tropical Cyclone Genevieve lingered between Hawaiʻi and surface high pressure to the north. Windward and mauka showers were slightly enhanced from the night of the 3rd through the 5th, particularly from Maui westward. Moderate to breezy trades returned on the 6th and 7th, with mainly isolated to scattered windward and mauka showers.

A wetter pattern developed from the 8th through the 10th as an upper-level trough northwest of the state combined with enhanced moisture associated with a tropical disturbance passing south of the islands. Showers increased first over windward portions of the Big Island on the 8th before spreading westward across southern and western Big Island, windward Maui County, and Oʻahu on the 9th, with some enhancement over Kauaʻi on the 10th. Three-day rainfall totals reached 3 to 7 inches on the Big Island, around 2 inches on Maui and Molokaʻi, 1 to 2 inches on Oʻahu, and around 1 inch on Kauaʻi. Showers tapered off through the 11th and 12th, with drier conditions and minimal windward rainfall by the 13th.

The most significant weather event of the month occurred from the 14th through the 17th in the form of Tropical Cyclone Lala. Breezy to locally windy trades and generally dry conditions prevailed over most of the state on the 14th, although moisture ahead of Tropical Storm Lala enhanced showers along the windward coasts and mountain slopes of Maui and the Big Island. Rainfall totals ranged from 1 to 3 inches on Maui and around 2 to 6 inches on the Big Island. Winds rapidly increased that night, with tropical-storm-force gusts observed over and leeward of island terrain from Oʻahu eastward.

Conditions deteriorated rapidly from east to west on the 15th as Lala strengthened into a hurricane and passed within 50 miles of the southern tip of the Big Island. Torrential rain began affecting the east and southeast Big Island around midmorning, with rainfall rates generally 2 to 4 inches per hour, but locally higher. Nearly 24 hours of intense rainfall produced 15 to 30 inches across the Hāmākua, Hilo, Puna, and Kaʻū Districts, with the highest totals exceeding 3 feet in portions of southeastern Kaʻū and the Laupāhoehoe area in the northeast. Most of the rain fell within about 15 hours, from 9 AM on the 15th through midnight on the 16th, with a 3-hour rainfall corresponding to a 50- to 100-year recurrence interval for a couple spots near Volcano. This one system dropped enough rain in a couple of days to cause most stations statewide to come in well above average for August. Additionally, for most places, this storm accounted for a significant percentage or nearly all of their monthly rainfall.

The extreme rainfall caused significant rises along streams, landslides, and considerable flash flooding, particularly around Pāhala and Nāʻālehu. Floodwaters pushed two homes off their foundations, while numerous other homes and buildings sustained water and wind damage. Flooding destroyed or damaged roads, bridges, and other critical infrastructure along and near Highway 11, effectively cutting off communities in the area from the rest of the island. Direct fatalities were reported in Nāʻālehu as a result of the flooding, and other important community facilities, including schools and the Nāʻālehu cemetery, sustained severe damage. Heavy rainfall also spread to windward Maui later on the 15th, with 24-hour totals around 8 to 12 inches and locally higher amounts near 16 inches.

The heavy rain associated with Lala spread across the remainder of the state late on the 15th and through the 16th. Rainfall rates generally ranged from 1 to 3 inches per hour, with the heaviest rain concentrated along windward areas. Maui and Oʻahu received roughly 5 to 10 inches on the 16th, while Kauaʻi and the remainder of Maui County received around 3 to 8 inches. Two Oʻahu stream gages, Mānoa Stream at Woodlawn Drive and Waikāne Stream, recorded their highest peak water levels in their periods of record. Significant flooding and landslides resulted in numerous road closures, including North Kīhei Road on Maui, portions of the H-1 Freeway and Pali Highway on Oʻahu, and portions of Kūhiō Highway near Hāʻena Beach Park, Wainiha Powerhouse Road, and the Hanalei River bridge area on Kauaʻi.

Rainfall gradually diminished as Lala moved west of the state, although lingering moisture produced another couple of inches of rain across many windward areas over the following days. A brief return to drier trade wind weather on the 18th gave way to weaker winds through the 21st as a trough passed northeast of the state. Isolated to scattered windward showers continued statewide, while some enhanced leeward showers developed along the Kona coast and lower slopes of the Big Island, particularly between Kailua-Kona and Miloliʻi, with localized rainfall totals of 1 to 3 inches. Trade winds increased to breezy to strong speeds from the 22nd through the 24th as Tropical Storm Moke passed from east to west to the south of the islands. Moke was smaller and remained farther south than Lala, resulting in considerably lower rainfall totals, generally 1 to 3 inches and focused primarily over windward areas.

Moderate to locally breezy trades returned from the 25th through the 29th, with mostly light windward and mauka showers and dry leeward conditions. Increased low-level moisture produced somewhat more active trade showers over windward higher elevations of Maui and the Big Island on the 27th and 28th, spreading to Oʻahu and Kauaʻi by the 29th. Rainfall totals over this period generally ranged from 1 to 2 inches. Breezy trades and mostly dry conditions rounded out the month.

Island of Kauaʻi : [August 2026 map] [year-to-date map]

Hurricane Lala certainly had an impact on the rainfall in August, with nearly all of the sites on the island coming in above average and a couple as high as 2 to 3 times their August averages. The few exceptions to this were along the eastern and western coastal areas with totals around 80 to 90% of average. The USGS gage on Mt. Waiʻaleʻale had the highest monthly total for the island with 37.67 inches (108% of average). The highest daily total for the island was measured at the USGS’ Kilohana RG with 10.46 inches on the 16th. This gage also had its wettest August since 2010).

The year to date (YTD) totals and percentages of average were above average at all stations this month, except one. The highest YTD total still belongs to Mt. Waiʻaleʻale with 335.85” (128% avg), which was also the state’s highest YTD rainfall. 

Island of Oʻahu: [August 2026 map] [year-to-date map]

Every site on the island had above average rainfall for August, with several over 200%. The Mānoa Lyon Arboretum had the highest total on the island again this month with 32.03 inches, (253% of average). The highest daily total came from the USGS’ Poamoho RG1 with 12.10 inches on the 16th. Nine stations turned in their wettest August in their respective periods of record: USGS Kamananui Stream (since 2012), Luluku Ua Net (record-since 1916, Missing data in 1996), Makua Range RAWS (since 2012), Mānoa Lyon Arboretum (record-since 1975), Pālehua RAWS (since 2010), Pūpūkea RG USGS (since 2012), Waiawa CF Ua Net (record-since 1992), Waiʻanae Boat Harbor (since 2004), and Waiʻanae Valley RAWS (since 2004).

The year to date (YTD) totals continue to run well above average for all reporting stations. The highest YTD total came from the USGS Moanalua RG with 172.13 inches (202% of average). 

Maui County: [Maui August 2026 map] [year-to-date map] [Molokaʻi/Lanaʻi August 2026 map] [year-to-date map]

All but one site in the county came in well above average for this month, with several as much as 6 to 10 times their typical August values! The USGS’ W. Wailuaiki Stream gage had the highest monthly total in the county with 39.76 inches (233% of average), as well as the highest daily total of 11.22 inches on the 16th. The Kahului Airport set a record daily rainfall record on the 15th with an amount of 0.29 inches (old record was 0.23 inches set in 1993). Four sites recorded their wettest August: Kaunakakai Mauka Ua Net (record-since 1991, Missing data in 2015 and 2025); Kula 1 RAWS (since 2010); Lahainaluna Ua Net (record-since 1991, Missing data 1993, 2003, and 2014); and Pukalani Ua Net (record-since 1992, Missing data in 2024).

The year to date (YTD) totals for all reporting sites in the county were all between 100 and 400 % of average thanks to an impressive August showing. The highest YTD total is still at Puʻu Kukui with 281.66 inches (109% of average). 

Island of Hawaiʻi: [August 2026 map] [year-to-date map]

All but one site on the island came in well above average for August. With most of the rain falling across the north through southeast portions of the island, these areas ended up with a rather impressive 500 to 1300% of their usual August values. In addition, nine sites (out of those included in this summary) recorded daily rainfall amounts of 20 inches or more on the 15th, including the highest amount on the island and statewide of 30.50 inches at the Nene Cabin RAWS. The USGS’ site at Kawainui Stream had the highest monthly total for the island again this month with 41.24 inches (462% of average). The Hilo Airport set a record daily rainfall record on the 15th with an amount of 6.82 inches (old record was 5.10 inches set in 1969). Several sites had their wettest August since Hurricane Lane in 2018, but came in second to those values. Thirteen sites recorded their wettest August this year: Kahua Ranch Ua Net: record-since 1992, Missing data in 2015); Kapāpala Ranch (since 1949); Kapāpala RAWS (since 2015, which beat their rainfall amount from Hurricane Lane in 2018); Kahuku Ranch RAWS (since 2016); Kamuela Upper Ua Net (record-since 1992); Kawainui Stream USGS (since 2010); Lower Kahuku RAWS (since 2015); Mauna Loa Observatory climate site (since 2005); Nene Cabin RAWS (since 2015); Puʻu Aliʻi RAWS (since 2012); Pāhala Ua Net (record-since 1991, Missing data in 2023); South Point NWS (since 2004, Missing data in 2011, 2024), and Waimea Plain SCAN (since 2012, Missing data in 2015).

All of the year to date (YTD) totals were near to above average for the island, with the exception of Puhe CS on the leeward Kohala coast at 68%. The highest YTD total was the USGS gage at Honoliʻi Stream with 219.47 inches (144% of average).

Data Sources: Data used in this report are from National Weather Service sources including climate network weather observation stations at Līhuʻe, Honolulu, Kahului, and Hilo, the Ua Net network of automated rain gages, and selected Cooperative Observer sites. Additional data come from automated rain gages operated by the State of Hawaiʻi Department of Land and Natural Resources, the U.S. Geological Survey (USGS), the U.S. Bureau of Land Management, the U.S. National Park Service, the Department of Defense, the U.S. Fish and Wildlife Service, and the U.S. Department of Agriculture, as well as manual observations from the Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS). Averages come from the National Centers for Environmental Information (1991-2020 series) and the Rainfall Atlas of Hawaiʻi (https://www.hawaii.edu/climate-data-portal/hawaii-climate-atlases/). Supplemental data used in some of the analyses are from the Hawaiʻi Climate Data Portal (https://www.hawaii.edu/climate-data-portal/). Data presented here are not certified and should be used for informational purposes only. 

Tina Stall
Senior Service Hydrologist 
NOAA/NWS Weather Forecast Office Honolulu