Cool ocean waters off the Delaware coast this Memorial Day weekend
As Memorial Day weekend marks the unofficial start of summer across Delaware, beachgoers at places like Rehoboth, Bethany, and Lewes are discovering that ocean temperatures are still far from summer-ready. Despite air temperatures climbing into the low 70s Fahrenheit (21–23°C), the Atlantic Ocean off Lewes is holding steady at a chilly 61.9°F (16.6°C).
This reading comes from the NOAA observation station in Lewes, where May averages typically hover around 60°F (15.5°C). While this is seasonally normal, the ocean’s slow warm-up often lags behind rising air temperatures due to water’s higher specific heat capacity. This means that although the air in Lewes peaks in July, water temperatures don’t reach their warmest until August, often leveling off in the low to mid-70s (22–24°C).
Unexpected cooling events, like the wind-induced upwelling seen in Atlantic City in July 2024, where temperatures dropped into the 50s (10–15°C), can also make swimming less inviting—even during the height of summer.
Cold water safety concerns
With water temperatures below 70°F (21°C), the National Center for Cold Water Safety urges caution. Immersion in cold water can lead to cold shock or even hypothermia. Swimmers are advised to exit the water immediately if they experience difficulty breathing or muscle paralysis, and to warm up quickly, as body temperature can continue to drop even after drying off.
Forecast at Delaware beaches
Holiday beachgoers can still enjoy the weekend under mostly sunny skies, with dry conditions and temperatures in the low 70s°F (around 22°C). But many might prefer staying on the sand instead of braving the cold surf, at least until June’s warmer currents roll in.
