Pool season · State index
Delaware Pool Season 2026: Opening & Closing Dates by City
Last updated: July 25, 2026 · 1 cities covered
Both halves of the pool year for all 1 covered Delaware cities. The median calendar runs April 19 to October 21. Every row links to a one-page season overview with the live water-temperature model; the opening and closing hubs carry the full checklists.
Delaware: a moderate-season pool state| City | Open by | Close by | 80°F+ days |
|---|---|---|---|
| Dover | Apr 19 | Oct 21 | 99 |
What the columns mean
"Open by" is the recommended spring date — two weeks before the city's 7-day mean temperature crosses 61°F, the model's proxy for water approaching the 65°F algae-growth zone. "Close by" is the fall deadline — ten days after the water leaves that zone, capped a week ahead of the local 50% first-freeze date. "80°F+ days" counts days whose normal high reaches 80°F: the length of the true warm-swim season, and the fairest single number for comparing Delaware cities against each other.
Every figure comes from each city's own NOAA 1991–2020 normals station (named in its guide's footer), so neighboring cities can legitimately differ by a few days. The season overview linked from each row adds the live water-temperature model and the full-year season bar; the state hubs above carry the step-by-step checklists.
Swim-season length across Delaware
The fairest way to compare Delaware cities is the number of days with 80°F+ normal highs — the practical warm-swim season. Every bar links to that city's one-page season overview with the live water model.
Delaware pool climate at a glance
Mid-Atlantic humidity drives a dependable summer season, and the Atlantic keeps Delaware's beach towns mild into early fall, often letting coastal pools outlast inland ones. In model terms that makes Delaware a moderate-season state. The spread shows up clearly on the local pages: compare Dover's pool season and the difference is measured in weeks, not days. Neighbors in the index run on their own normals too — see Connecticut and District of Columbia for the adjacent calendars.
Delaware pool season FAQ
When do pools open in Delaware?
Model openings in Delaware run from April 19 in Dover to April 19 in Dover, with the statewide median on April 19. Each date is two weeks before that city's 7-day mean temperature crosses 61°F — early enough to start up in algae-cold water.
When should you close a pool in Delaware?
The median Delaware closing deadline is October 21, and every city's own deadline is capped a week ahead of its NOAA 50% first-freeze date. Closing late and cold beats closing early and warm — cool water holds its winter chemistry far better.
Which Delaware city has the longest swim season?
Dover leads with 99 days of 80°F+ highs per year. The chart above ranks every covered city by the same metric.