Pool season · Maryland
Columbia Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Columbia 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.
Columbia, MD — 107 swim days a yearEach dot on the bar is one week of Columbia's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (April 10–May 1), solid teal is swim season, and hollow amber is the closing window ending October 21. The black marker is today — its position against the colors is the entire executive summary.
The Columbia pool calendar
Opening — target April 17
Open by April 17 — a two-week head start on the May 1 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 21
Hold the cover until October 11, then winterize by October 21, a week ahead of the November 9 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Columbia'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 36° | 35° | 41° | 51° | 61° | 70° | 78° | 79° | 75° | 65° | 53° | 43° |
Warmest water typically July–August (peaking near 79°F); heaters and covers shift any month up.
Every station tells its own story: compare this curve with Baltimore's pool season and Ellicott City's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Maryland season index.
Columbia pool season FAQ
When should I open my pool in Columbia, MD?
The site model recommends opening by April 17 — about two weeks before Columbia'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 Columbia opening guide.
When should I close my pool in Columbia?
Winterize by October 21. The model holds the deadline a week ahead of Columbia's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Columbia closing guide.
How long is the swim season in Columbia?
Columbia averages 107 days a year with normal highs of 80°F or better — right on the statewide median. The Maryland season index ranks all 9 covered cities by the same metric.
How warm does pool water get in Columbia?
An unheated pool near Columbia typically peaks around 79°F in high summer and bottoms out near 34°F in winter, spending roughly 1 month at or above the 78°F comfort line most swimmers prefer. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Columbia hits the closing window
Data: NOAA 1991–2020 climate normals via Laurel 3 W (8.3 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.