Pool season · Oregon
Hillsboro Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Hillsboro pool. The season bar below draws everything the model knows — opening window, prime season, closing window — against today's date, with the working details one click away on the opening and closing pages.
Hillsboro, OR — 58 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Hillsboro's swim season; the hollow teal run before it (May 27 to June 17) is when to open; the hollow amber run after is when to close, with September 30 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Hillsboro pool calendar
Opening — target June 3
Target June 3; the practical window runs May 27–June 17, and the 7-day mean crosses the 61°F threshold around June 17. Cold-water starts are the cheap ones.
Closing — deadline September 30
The window opens September 20 once water leaves the algae zone; the model deadline is September 30, a week ahead of the October 23 freeze normal.
Estimated water temperature by month
This is Hillsboro's typical-year water curve: the same EWMA model as the live widget, run on the 1991–2020 normals instead of this week's weather.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 40° | 41° | 44° | 48° | 54° | 59° | 64° | 68° | 65° | 57° | 48° | 42° |
The curve peaks near 68°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Gresham's pool season and Medford's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Oregon season index.
Hillsboro pool season FAQ
When should I open my pool in Hillsboro, OR?
Open by June 3 — the model places Hillsboro's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Hillsboro opening guide has the 12-step sequence.
When should I close my pool in Hillsboro?
Close by September 30: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Hillsboro closing guide sequences the work backward from that date.
How long is the swim season in Hillsboro?
Hillsboro averages 58 days a year with normal highs of 80°F or better — about 10 days later than the Oregon median. The Oregon season index ranks all 8 covered cities by the same metric.
How warm does pool water get in Hillsboro?
An unheated pool near Hillsboro typically peaks around 68°F in high summer and bottoms out near 40°F in winter, never quite reaching the 78°F comfort line without a heater or solar cover. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Hillsboro hits the closing window
Data: NOAA 1991–2020 climate normals via Portland-hillsboro Airport (1.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.