Note: The rainfall totals provided here are from online sources and have only basic quality control applied to remove obvious errors. The values from the data sources may change in the future as corrections are made by the responsible data custodians.
I hope everyone had a nice Christmas holiday! As mentioned in my last post on December 19th, this week’s post would be just a short update to provide the latest numbers from last week’s heavy rain event since it was still ongoing last Friday. I have to say there actually wasn’t too much heavy rain, but the pattern was essentially stationary and kept repeated bouts of rainfall over Kauaʻi County and Oʻahu. Maui County and the Big Island ended up being quite a bit drier, just as the models forecasted over a week in advance.
So without additional blah, blah, blah, here are the final totals, in various forms, from the December 14th through 20th event. The map below shows the 7-day totals as derived by the Multi-Radar/Multi-Sensor (MRMS) system combining radar rainfall estimates with rain gage data. The image looks very similar to the 5-day map but with additional rainfall filled in mainly over Oʻahu and the Kauaʻi Channel. The highest amounts, greater than 8 inches, are within the main band extending from west Oʻahu toward the southwest. Recall from last week’s post that the numbers over the mid-section of the state are degraded due to the lack of data from the Molokaʻi WSR-88D radar, which has been out of service for quite a while. While the numbers may be off, it provides a decent look at the overall pattern of rainfall over and around the islands.
MRMS 7-day accumulated precipitation covering December 14th through December 20th. The MRMS website only provides up to 3-day totals so the data in this graphic were downloaded from the MRMS repository on the Registry of Open Data on AWS and processed using QGIS software.
A better look at the rainfall over the islands comes from the Hawaiʻi Climate Data Portal’s (HCDP) daily rainfall grids. This analysis incorporates more rain gage data than the MRMS view and provides output at a higher resolution than the MRMS data. You can easily see the huge differences in rainfall between the west and east halves of the state. Large portions of Kauaʻi and Oʻahu had 2 to 8 inches, with a peak total of more than 14 inches over west Oʻahu (Kaʻala). Meanwhile, most of the Big Island and Maui County received less than half an inch of rainfall for the entire week!
Map of gridded rainfall in inches for the 7-day period from December 14th through 20th, 2025. The data come from the HCDP daily rainfall data grids.
For a better look at the details of where the highest amounts were observed last week, the table below shows the top five 7-day rain gage totals for each county. Below the table are maps of the top 5 totals on Kauaʻi and Oʻahu. I didn’t include maps for Maui County and the Big Island because…why bother.
| Station | Dec 14-20, 2025 Rain (inches) |
| Kauaʻi | |
| Waiʻaleʻale | 7.49 |
| Puʻu Lua | 6.77 |
| Mōhihi Crossing | 6.74 |
| Waiʻalae Rain Gage | 6.31 |
| Līhuʻe Airport | 6.24 |
| Oʻahu | |
| Kaʻala | 14.24 |
| Maunawili | 9.80 |
| Mākaha Stream Rain Gage | 9.73 |
| Palisades | 9.60 |
| Pālehua | 9.23 |
| Maui County | |
| Keokea | 1.27 |
| Anapuka | 1.01 |
| Puʻu Aliʻi | 0.91 |
| Hāmoa | 0.89 |
| Lānaʻi City | 0.84 |
| Big Island | |
| Kaiholena | 1.76 |
| Pali 2 | 1.25 |
| Kapāpala Ranch | 1.18 |
| Kapāpala Ranch RAWS | 0.97 |
| Keahuolū | 0.94 |
Top 5 rain gage totals for each county across the state of Hawaiʻi. The totals were obtained from the HCDP via online request and from HFO’s website (for the main airports). I applied a very basic quality control to filter out known bad data values. For example, a rain gage in Mākua Valley was listed as having no rainfall the entire week, which is obviously invalid.
Plot of the top 5 rainfall totals on Kauaʻi for the December 14th through 20th period.
Same as above, but for Oʻahu.
The week of rainy conditions ensured that the climate monitoring sites at the main airports on Kauaʻi and Oʻahu would have above average totals for December 2025. Through the first 20 days of the month, Līhuʻe Airport, Honolulu Airport, and Kalaeloa Airport already have totals that have exceed the average for the entire month of December. Kahului Airport on Maui, and Hilo Airport and Kona Airport on the Big Island are well below average for December rainfall.
| Station | Dec Total thru 12/20 | % Dec Avg thru 12/20 | % of Full Dec Avg |
| Kauaʻi | |||
| Līhuʻe Airport | 6.92 | 231% | 149% |
| Oʻahu | |||
| Honolulu Airport | 4.77 | 338% | 219% |
| Kalaeloa Airport | 4.77 | 322% | 208% |
| Maui County | |||
| Kahului Airport | 0.19 | 11% | 7% |
| Big Island | |||
| Hilo Airport | 1.87 | 24% | 15% |
| Kona Airport | 0.21 | 31% | 20% |
Rainfall totals for the month through December 20th at the main airport climate monitoring sites. Also included are the totals expressed as a percent of the average December rainfall through the 20th (third column), and as a percent of average for the entire month of December (fourth column). The rainfall totals are from HFO’s website and the average values are from the National Centers for Environmental Information (NCEI), 1991-2020 series.
The last graphic I want to show highlights the large differences between the wet western half of the state and the dry eastern half. This is the USGS’ 7-day average streamflow color coded by percentile classes. The data used in the map are as of December 19 and all of the available sites on Kauaʻi and Oʻahu are in the normal or higher classes. On the other hand, all of the sites on the Big Island and Maui County are below normal, with most sites in the much below normal class.
Map of 7-day average streamflow as of December 19, 2025 from USGS gages across the state. Percentile classes are listed at the bottom. Unfortunately, I forgot to download the map for December 20th, but I’m sure it’s not a whole lot different from this one.
From a drought relief perspective, it would have been nice if last week’s event covered the entire state but I guess we’ll have to take what we can. The extended range outlooks into early February are still suggesting wetter than normal conditions over the state so hopefully the Big Island and Maui County will get their turn as well.