Pool Season

National Pool Closing Day and Opening Day

The dates for the next three years, where the two days came from, and why your pool may need a different one.

Updated November 2026

Short answer

National Pool Opening Day is the last Saturday in April: April 24, 2027. National Pool Closing Day is the third Saturday in September: September 18, 2027.

Both are promotional dates, not rules. The right day for your pool depends on water temperature where you live.

Find your closing window by state

For spring, see when to open your pool.

What are the dates each year?

National Pool Opening Day and National Pool Closing Day dates
Year	National Pool Opening Day	National Pool Closing Day
2026	Saturday, April 25	Saturday, September 19
2027	Saturday, April 24	Saturday, September 18
2028	Saturday, April 29	Saturday, September 16

Opening Day is always the last Saturday in April. Closing Day is always the third Saturday in September.

Where did these days come from?

National Pool Opening Day was started in 2016 by a national pool supply retailer and is listed by National Day Calendar. National Pool Closing Day followed as its fall counterpart and is promoted mainly by pool retailers.

Neither is an official holiday. They are reminders to stock up and get the work done, timed for the middle of the country.

Should I open and close on those days?

Only if they happen to match your weather. Algae grows once water warms past about 60 degrees, so the goal is to open before that and close after the water has cooled for good.

How the national days compare with temperature-based timing by region
Where you live	Opening Day, late April	Closing Day, mid September
Deep South and Gulf Coast	Too late. Water is already warm	Far too early
Mid-Atlantic, Midwest, lower Northeast	About right	Usually two to five weeks early
Northern states and mountains	Often a little early	About right

The rule behind this: open before the water reaches 60 degrees, and close once it stays below 65 degrees.

Closing while the water is still warm is the most common reason a pool opens green in spring. The state tables for closing and opening give a date range for 75 cities, built from 30 years of climate records. Whichever dates you choose, have the basics on hand first: a winter cover and a plug kit for closing, and a test kit for opening.

Frequently Asked Questions

When is National Pool Opening Day 2027?

Saturday, April 24, 2027. It falls on the last Saturday in April each year.

When is National Pool Closing Day 2027?

Saturday, September 18, 2027. It falls on the third Saturday in September each year.

Is National Pool Closing Day too early to close my pool?

For most of the country, yes. In mid September the water is still above 65 degrees in most states, and a pool closed warm can turn green under the cover.

Is there a best day to open a pool?

There is a best window, not a single day. Open before the water reaches 60 degrees. That is March in the South and May in the far North.

Sources

National Day Calendar: National Pool Opening Day

Pick your own dates

See when the water in your state crosses the temperatures that matter.

When to Open Your Pool When to Close Your Pool