Hillsboro: Airport Gets 0.82 Inch of Rain in October, Its Second-Driest Since 1999
- Hillsboro Airport recorded 0.82 inch of rain in October, 24% of the 3.37 inches that normally falls in the month, the National Weather Service's monthly climate report for Hillsboro shows.
- Among the 28 complete Octobers in the airport station's record, 1999 through 2026, that makes this the second-driest October, the second-warmest by average high and the second for 80-degree days, a F…
- The normals are NOAA's official 1991–2020 averages for the airport, published by the National Centers for Environmental Information.
Hillsboro Airport recorded 0.82 inch of rain in October, 24% of the 3.37 inches that normally falls in the month, the National Weather Service’s monthly climate report for Hillsboro shows. Highs averaged 68.5 degrees, 4.8 above normal, and the airport reached 80 or warmer on eight days.
Among the 28 complete Octobers in the airport station’s record, 1999 through 2026, that makes this the second-driest October, the second-warmest by average high and the second for 80-degree days, a Focus Hillsboro review of NOAA daily data found. The weather service issued the monthly report Nov. 1, and its figures are preliminary.
How this October stacks up
The normals are NOAA’s official 1991–2020 averages for the airport, published by the National Centers for Environmental Information. For October they are 3.37 inches of rain, an average high of 63.7 and an average low of 40.9. The weather service’s monthly report uses the same figures.
For the rankings, we totaled every October in the station’s daily record in NOAA’s Applied Climate Information System. That record begins in June 1998, but October 1998 is missing eight days, so the comparison starts in 1999.
| October of… | Rain (in.) | Avg. high (°F) | Avg. low (°F) | Days at 80°F+ |
|---|---|---|---|---|
| 2026 | 0.82 | 68.5 | 41.2 | 8 |
| NOAA normal, 1991–2020 | 3.37 | 63.7 | 40.9 | — |
| 2002 (driest) | 0.43 | 63.6 | 37.4 | 1 |
| 2013 (3rd-driest) | 0.87 | 63.7 | 37.5 | 0 |
| 2006 (4th-driest) | 0.90 | 63.5 | 37.5 | 0 |
| 2022 (warmest highs) | 2.53 | 71.7 | 44.1 | 12 |
| 2015 (3rd-warmest highs) | 3.42 | 67.7 | 45.7 | 2 |
Our compilation from NOAA ACIS daily data for station Portland-Hillsboro AP (KHIO), full Octobers 1999–2026; ranks are among those 28 years. NOAA’s normals for the station do not include a count of 80-degree days. From 1999 to 2025, the station averaged 1.1 such days per October (our calculation).
Only 2002 was drier, and only 2022 was warmer by day. That year also had 12 days at 80 or above, the only October count higher than this year’s eight. In 16 of the 27 Octobers from 1999 to 2025, the airport never reached 80 at all, our count shows.
Nights stayed closer to normal. The average low of 41.2 was 0.3 degree above normal and ranks 17th of the 28 years. The airport fell to 31 on Oct. 23, 29 on Oct. 24 and 32 on Oct. 31, three nights at or below freezing against a normal of 2.9, the monthly report shows.
Three dry weeks, then one wet one
The two coldest nights came near the end of a long dry run, and most of the month’s rain fell after it. Through Oct. 24, the airport had collected just 0.04 inch, with none measurable from Oct. 11 through Oct. 24, NOAA’s daily data show.
Then 0.78 inch fell from Oct. 25 through Oct. 30, led by 0.31 inch on Oct. 25, the month’s wettest day. Oct. 31 stayed dry, so the total did not change. October ended with seven days of measurable rain, meaning 0.01 inch or more, against a normal of 14.9.
The shortfall carries through the year. The weather service’s daily summary for Oct. 31 lists 17.57 inches at the airport since Jan. 1, against a normal of 24.44 by that date. That is 72% of normal, by our calculation.
Abnormally dry, not in drought
That rain deficit has not put Washington County into drought on the weekly U.S. Drought Monitor map. The map released Thursday, Oct. 29, with data valid Oct. 27, places the whole county in category D0, “abnormally dry,” according to the monitor’s county statistics.
The monitor uses D0 for areas “showing dryness but not yet in drought,” or recovering from it. The county has been 100% abnormally dry on every weekly map since Sept. 29, up from 99.77% on the four September maps before that. Statewide, the Oct. 27 map shows 88.3% of Oregon in drought at level D1 or worse.
The monitor releases a new map every Thursday, using data through the previous Tuesday morning.
Stored water is a separate measure from the monitor’s map. Henry Hagg Lake ended the water year on Sept. 30 at 36.6% full, Focus Hillsboro reported Oct. 28 from a Joint Water Commission packet.
A cool, dry start to November
November has opened without rain so far. The airport recorded no rain on Nov. 1 or Nov. 2, and its Nov. 1 high of 45 was 12 degrees below normal, the weather service’s daily climate summary for Nov. 1 shows.
Top image: Illustrative image, 2018: fallen bigleaf maple leaves on the Molalla River in Oregon. Photo: Greg Shine, BLM Oregon & Washington, public domain, via Wikimedia Commons (cropped).
