Pool season · Oregon
Gresham Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
This is the one-page view of Gresham's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
Gresham, OR — 58 swim days a yearEach dot on the bar is one week of Gresham's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (May 8–May 29), solid teal is swim season, and hollow amber is the closing window ending October 7. The black marker is today — its position against the colors is the entire executive summary.
The Gresham pool calendar
Opening — target May 15
Open by May 15 — a two-week head start on the May 29 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 7
Hold the cover until September 27, then winterize by October 7, a week ahead of the November 20 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Gresham'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 41° | 43° | 47° | 50° | 56° | 62° | 67° | 70° | 67° | 60° | 51° | 44° |
The curve peaks near 70°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Eugene's pool season and Hillsboro's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Oregon season index.
Gresham pool season FAQ
When should I open my pool in Gresham, OR?
The site model recommends opening by May 15 — about two weeks before Gresham's 7-day mean temperature crosses 61°F, while the water is still too cold for algae. The step-by-step sequence is in the Gresham opening guide.
When should I close my pool in Gresham?
Winterize by October 7. The model holds the deadline a week ahead of Gresham's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Gresham closing guide.
How long is the swim season in Gresham?
Gresham averages 58 days a year with normal highs of 80°F or better — about 9 days earlier than the Oregon median. The Oregon season index ranks all 8 covered cities by the same metric.
How warm does pool water get in Gresham?
An unheated pool near Gresham typically peaks around 70°F in high summer and bottoms out near 41°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 Gresham hits the closing window
Data: NOAA 1991–2020 climate normals via Portland Troutdale Airport (3.7 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.