October 2026 Monthly Rainfall Summary for Hawaii

Monthly Precipitation Summary 

State of Hawaii 

Month: October 2026

Prepared: November 5, 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: October was bookended by a few complex weather patterns, including several periods of enhanced rainfall.

State: [Text data table for rain gages]

Tropical Storm Nolo gradually accelerated westward away from the state to start the month, but residual tropical moisture drawn up over the islands in breezy southeast flow maintained increased showers for the first couple of days, mainly for Kauaʻi and Oʻahu. Despite some rises in stream levels, rainfall rates in the 1 to 2 inch per hour range and fairly quick-moving showers helped to keep flooding impacts to a minimum. Drier and more stable conditions returned as high pressure rebuilt over the state, bringing light to moderate trade winds through the first week of the month.

Another period of unsettled weather occurred between the 7th and 9th as a result of a complex atmospheric pattern. A strong upper-level low and an associated surface low developed northwest of the islands on the 7th, increasing instability and drawing tropical moisture northward over the state. This southerly flow also drew a tropical disturbance up over the islands from the southwest, adding to the available moisture. Scattered showers, some locally heavy, developed over Kauaʻi and Oʻahu on the night of October 7th. A band of intense rainfall moved through the Kauaʻi Channel and over Oʻahu and portions of Molokaʻi on October 8th, bringing multiple rounds of heavy showers and gusty southerly winds. Rainfall rates mainly stayed in the 0.5 to 2-inch per hour range, though some heavier rates were observed at times. Flooding impacts were mostly seen on Oʻahu and mainly consisted of nuisance ponding on roads and moderate rises in stream levels. The exception was on the North Shore of Oʻahu where Kamehameha Highway was flooded in a few spots between Pūpūkea and Turtle Bay with up to a foot of water flowing over the road. In addition, both lanes of Waialua Beach Road were flooded near the intersection with Komo Street. Scattered showers, some locally heavy, were observed on the other islands as well during this event, though no significant flooding occurred. Dry air moved in from west to east following this band, decreasing rainfall first for Kauaʻi the previous night and then Oʻahu by the following evening. Lingering moisture allowed weaker and less widespread showers to continue at times through the 9th. 

More typical, moderate to breezy trade wind conditions returned through the middle of the month, bringing generally dry conditions and light showers focused along windward slopes. A brief increase in showers affected windward Maui and the Big Island on the 12th, while several weak disturbances brought occasional enhancements to windward showers between the 17th and 21st. Light to moderate trades and relatively few showers dominated through the 26th.

The final several days of October brought the most significant rainfall and flooding of the month as widespread deep tropical moisture and increasing atmospheric instability affected the islands. Shower activity increased from west to east across the island chain from the 27th through the 28th as an upper-level low west of Kauaʻi drew a surface trough and deep tropical moisture up over the islands from the southwest. This trough was an extension of the monsoon trough. While typically a Western Pacific feature, it can extend farther east into the Central Pacific during strong El Niño summers. Precipitable water values over the islands during this event were around 1.5 times the normal amounts seen in late October, with higher values farther to the southwest. 

As the upper trough moved closer to the state, instability increased and tapped into the anomalously high moisture to fuel bands of heavy showers and thunderstorms along the corresponding surface trough. The first bands of moderate to heavy rain set up over the Kauaʻi Channel during the afternoon of the 27th, then spread eastward through the evening and overnight with rainfall totals around 0.5 to 1.5 inches across Oʻahu. The bulk of the heavy rain shifted eastward over Maui County and the Big Island on the 28th, concentrated along three main focus features: a nearly-stationary convergent boundary in the Kaʻiwi Channel, a diffuse surface trough across Maui County and the Alenuihaha Channel, and southeast flow into the Kaʻū, Puna, and Hilo Districts. Rainfall totals on the 28th ranged from 0.5 to 2 inches on Oʻahu and the Big Island to 1 to 4 inches across Maui County, with isolated amounts up to 6 to 8 inches on windward Molokaʻi and Maui. 

The diffuse trough shifted slightly eastward on the 29th, bringing additional periods of moderate to heavy showers over mainly Maui and the Big Island. Prevailing light to moderate trade winds focused most of the rainfall over windward areas which picked up an additional 2 to 6+ inches that day. Despite plentiful low-level moisture across the state, drier mid-level air moved in over the western half of the state, helping to keep showers on the lighter side, then spread over the remainder of the state overnight, with showers generally tapering down everywhere. 

A generally drier pattern settled across the state for the 30th and 31st. However, with a very moist airmass still in place and moderate trade winds dominating, scattered showers continued to focus along windward and mauka areas of the islands. Quick shots of embedded heavier rain moved through at times, enhanced by instability from an approaching upper-level trough. This was most significant on the 31st as heavy showers became anchored over the windward higher terrain of Kauaʻi and Oʻahu, producing totals around 1 to 3 inches on Oʻahu and 2 to 5 inches on Kauaʻi. Higher rainfall rates and rapid rises in the Hanalei and South Fork Wailua Rivers on Kauaʻi resulted in flash flooding which closed Kūhiō Highway near the bridge in Hanalei and piled up fallen trees from upstream against the Kūhiō Highway bridge in Wailua.

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

Kauaʻi had another solid rainfall showing in October owing to a few significant events, most notably on Halloween. Nearly all reporting stations came in well above average for the month, including several with totals around double their October averages. The USGS gage on Mt. Waiʻaleʻale had the highest monthly total for the island and the state with 50.05 inches (148% of average), which also made it the wettest October in its period of record (since 2003). The highest daily total for the island, however went to the nearby North Wailua Ditch USGS site with 11.68 inches on the 31st. The Līhuʻe Airport set a daily rainfall record with 1.08 inches on the 8th (old record was 0.61 inches set in 2025). The Hanalei Ua Net site (since 1997) and the North Wailua Ditch (since 2011) and Mt. Waiʻaleʻale (since 2003) USGS sites all had the wettest October in their respective periods of record. The Port Allen NWS HSOIS site also recorded its wettest October since it began in 2004 (missing data in 2009 and 2011).

The year to date (YTD) totals and percentages of average were all still above average this month. The highest YTD total for the county and the state was Mt. Waiʻaleʻale with 454.58 inches (139% avg).

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

Nearly all of the reporting sites had above average rainfall for October, with a large portion in the 200 to 400% range. The few sites that came in below average (70 to 80%) were on the leeward side of the Koʻolau Mountains. The highest monthly total occurred at the USGS Poamoho RG1 with 26.14 inches, (133% of average). This site also had the wettest October in its period of record (since 2012). The highest daily total came from the USGS Kamananui RG with 9.50 inches on the 8th. This site also had the wettest October in its period of record (since 2012). Eleven other sites on the island had their wettest October in their respective periods of record as well: Kuaokalā RAWS: since 2012 (missing data in 2015); Kahana Stream RG (USGS): since 2011; Kunia Ua Net: since 1991 (missing data in 2025); Olomana Fire Station Ua Net: since 1991; Poamoho Ua Net: since 1991; Punaluʻu Stream (USGS): since 2010; Pūpūkea RG (USGS): since 2012; Schofield Barracks Ua Net: since 2003; Tunnel RG (USGS): since 2013; and Wheeler AAF Ua Net: since 1997 (missing data in 2024 and 2025). Kahuku Ua Net also had its wettest October since 1965 (missing data in 2009 and 2024), which was also the 2nd wettest in its whole period of record (since 1905).

The available year to date (YTD) totals are all near to above average as well. The highest YTD total for the island came from the USGS Moanalua RG with 213.38 inches (202% of average). 

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

All but one site in the county (on leeward Lanai) came in above average for this month, with several around 2 to 4 times their typical October values. The USGS West Wailuaiki Stream site had the highest monthly total in the county with 36.55 inches (213% of average), as well as the highest daily total of 7.42 inches on the 29th. This site also recorded the wettest October since 2016. It was also the wettest in its entire period of record (since 2003), with the caveat of missing data from 2011 through 2015. The Kahului Airport set a daily rainfall record with 1.14 inches on the 28th (old record was 0.33 inches set in 1982. The Kahakuloa (since 1995, with missing data in 2021) and Wailuku (since 2012) Ua Net sites had the wettest October in their respective periods of record.

The year to date (YTD) totals for all reporting sites in the county were still between 100 and 400% of average. The highest YTD total remains at Puʻu Kukui with 313.87 inches (112% of average). 

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

The majority of sites came in above average for October, though not as much so as in September. The sites that came in below average for the month (mainly around 50 to 80%, though a few were under 30% and even under 10%) were mostly located in the interior of the island as well as a couple on the leeward coast. The somewhat odd distribution of above and below average sites could be due to the very isolated nature of some of the heavy rain and the complex weather patterns this month. The USGS site at Honoliʻi Stream had the highest monthly total for the island again this month with 40.97 inches (227% of average) and the highest daily total for the island and the state with 15.78 inches on the 29th. The Hilo Airport set a record daily rainfall record with 1.78 inches on the 29th (old record was 1.76 inches set in 2019). The USGS Kawainui Stream recorded the wettest October in its period of record (since 2010).

All but a few of the year to date (YTD) totals were near to above average for the island this month. The highest YTD total was the USGS gage at Honoliʻi Stream with 303.41 inches (161% 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