Mastic Beach — Water Temperature, Sea Conditions & Trends
This page provides clear and up-to-date information about water temperature for Mastic Beach (New York, United States). It includes the current water temperature, daily data for the last month presented in a simple chart, and a 7-day forecast. The page also compares today’s value with typical averages for this period, shows usual monthly ranges during the year, and lists nearby beaches with short descriptions. Local weather for the next few days and general details about Mastic Beach help you plan your visit and choose the best time for swimming.
Current Water Temperature
Water temperature in Mastic Beach in the Atlantic Ocean today is 23°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
✅ As of today, the minimum water temperature ranges from 68°F (20°C) to 74°F (23°C). The water is warm and pleasant for swimming, and in this range, one can stay in the water for extended periods without the risk of hypothermia. This is the ideal temperature for relaxation, swimming, and water sports. Families with children, as well as outdoor enthusiasts, will enjoy swimming and time spent in the water. For most people, this is the optimal temperature for a comfortable beach experience.
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 at this location is slightly warmer than average for this day in previous years.
According to our forecast, Water temperature in Mastic Beach will be 22.7°C in the next 7 days. See the table below for daily data for the upcoming week.
Table of Daily Sea Temperature Data
| Date | Current | Average | Forecast |
|---|---|---|---|
| JUN 27 | 18.5°C | 14.0°C | |
| JUN 28 | 18.8°C | 14.0°C | |
| JUN 29 | 20.2°C | 14.3°C | |
| JUN 30 | 20.4°C | 20.0°C | |
| JUL 1 | 20.6°C | 20.3°C | |
| JUL 2 | 21.2°C | 20.3°C | |
| JUL 3 | 21.0°C | 20.8°C | |
| JUL 4 | 20.9°C | 21.0°C | |
| JUL 5 | 22.8°C | 21.0°C | 22.8°C |
| JUL 6 | 21.0°C | 22.8°C | |
| JUL 7 | 21.3°C | 22.8°C | |
| JUL 8 | 21.5°C | 22.7°C | |
| JUL 9 | 21.8°C | 22.7°C | |
| JUL 10 | 22.0°C | 22.7°C | |
| JUL 11 | 21.5°C | 22.7°C | |
| JUL 12 | 21.8°C | 22.7°C |
* Current - Actual water temperature value
** Average - Average water temperature on this day in recent years
*** Forecast - Our water temperature forecast
Actual nearshore water temperatures may fluctuate by several degrees from the reported values, especially following heavy rainfall or extended periods of strong winds. Certain wind patterns can cause colder, deeper waters to rise and replace the sun-warmed surface water, leading to noticeable variations.
Our forecast is based on a proprietary mathematical model that considers real-time water temperature changes, historical trends, key weather patterns, wind strength and direction, and air temperature specific to each region. Additionally, we incorporate data from other resorts to enhance accuracy.
Water temperature data for this location is gathered from various sources, including buoys and satellite sea and ocean surface maps provided by the NOAA agency. We also incorporate data from local authorities in each specific location worldwide to ensure more accurate temperature readings.
Annual Water Temperature Overview by Month
Monthly Water Temp Ranges
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.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 2°C | 6°C | 9°C |
| February | 2°C | 5°C | 7°C |
| March | 2°C | 5°C | 8°C |
| April | 4°C | 7°C | 12°C |
| May | 8°C | 12°C | 17°C |
| June | 13°C | 18°C | 23°C |
| July | 18°C | 22°C | 26°C |
| August | 20°C | 23°C | 26°C |
| September | 18°C | 21°C | 25°C |
| October | 13°C | 18°C | 22°C |
| November | 9°C | 14°C | 18°C |
| December | 5°C | 9°C | 13°C |
* Click on a month to view detailed water temperature data.
Mastic Beach: Weather Forecast
July 6
July 7
July 8
Location, Beaches & Local Information
Nearby Beaches & Facilities
Smith Point County Park
Holiday Beach
Ho-Hum Beach Marina
Bellport Beach
Cupsoque Beach
Swimming Conditions
Swimming at Mastic Beach is most comfortable in midsummer when bay temperatures approach the low to mid‑20s °C and conditions are calmer than the open ocean, which suits families and casual paddlers. The bay’s shallow nature warms quickly on sunny days but also cools fast after cold spells, so early‑ and late‑season dips may feel brisk and some swimmers use wetsuits for longer stays in cooler months. Lifeguard coverage, beach access points, and water‑quality advisories vary by season and location, and swimmers should check local conditions, posted notices and boat traffic in the bay before entering the water to ensure a safe, enjoyable beach holiday.