Mastic Beach — Water Temperature, Sea Conditions & Trends

Water Temperature: Daily Trends, Historical Records, and Forecast

⚠️ As of today, the minimum water temperature ranges from 60°F (15°C) to 65°F (18°C). The water is comfortable for most people, making it an ideal range for water sports enthusiasts. The temperature does not cause significant discomfort, and swimming will be pleasant for the majority. However, it's important to remember that prolonged exposure to the water can still lead to cooling, so it's essential to monitor the time spent in the water, especially for children or elderly people.

It is important to note that these swimming tips and recommendations apply only in good weather. When the air temperature is below 68°F (20°C), and sometimes even below 77°F (25°C), swimming can be unpleasant even with relatively high water temperatures.

Water Temperature Chart Over the Last 30 Days

Water temperature in Mastic Beach has risen over the last week and month. Currently, the sea water temperature at this location matches the average for this day in previous years.

According to our forecast, Water temperature in Mastic Beach will be 18.2°C in the next 7 days. See the table below for daily data for the upcoming week.

Table of Daily Sea Temperature Data

Annual Water Temperature Overview by Month

Monthly Water Temp Ranges

30°C

25°C

20°C

15°C

10°c

5°C

0°C

Annual Water Temperature Trend

Mastic Beach sits on Long Island’s south shore along the shallow waters of the Great South Bay, offering a sheltered coastal setting influenced by tides, shallow depth and nearby inlets. Water temperatures there follow the seasonal cycle typical of temperate northeastern estuaries: in winter months water commonly ranges near 0–5°C, making swimming uncommon without thermal protection; spring brings a steady rise, roughly 5–15°C by late spring; peak summer conditions occur in June through August when bay temperatures generally reach about 18–25°C, occasionally slightly higher during heat spells; autumn sees a gradual cooling, with waters typically falling to around 10–20°C as daylight shortens and air temperatures drop. Local weather, wind, and freshwater runoff can produce short-term variability within these bands.