Pool season · Texas
San Marcos Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
San Marcos's whole pool calendar, condensed: when the water warms, when it cools, and where today falls between those edges. Use the opening guide and closing guide for the step-by-step work; keep this page for the dates.
Each dot on the bar is one week of San Marcos's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (February 22–March 15), solid teal is swim season, and hollow amber is the closing window ending November 21. The black marker is today — its position against the colors is the entire executive summary.
The San Marcos pool calendar
Opening — target March 1
Target March 1; the practical window runs February 22–March 15, and the 7-day mean crosses the 61°F threshold around March 15. Cold-water starts are the cheap ones.
Closing — deadline November 21
The window opens November 11 once water leaves the algae zone; the model deadline is November 21, a week ahead of the November 29 freeze normal.
Estimated water temperature by month
This is San Marcos'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 51° | 52° | 58° | 65° | 72° | 80° | 83° | 85° | 83° | 75° | 65° | 56° |
Warmest water typically June–September (peaking near 86°F); heaters and covers shift any month up.
Email me when San Marcos hits the closing window
Data: NOAA 1991–2020 climate normals via San Marcos (1.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.