Stony Brook water temperature
Stony Brook, RT 20 at Waltham, Massachusetts · River
The current water temperature at Stony Brook is 18.7 °C (as of September 21, 2026, source: USGS).
A river can change temperature within hours — snowmelt, rain or power-plant operations show up immediately. That is why the measured value counts here, not an estimate.
Measurement series & statistics
This measurement series includes 436 data points since July 23, 2026.
Lowest recorded value: 18.7 °C on September 21, 2026 · highest value: 27.4 °C on August 8, 2026.
In September, temperatures have ranged between 18.7 °C and 24.2 °C.
The current value is 3.2 °C below the September average of this series.
Nearby waters
More measuring points: Stony Brook
Frequently asked questions
Can you swim at Stony Brook right now?
The current water temperature is 18.7 °C. See live swimming conditions, weather and quality in the BrrChecker app.
How warm is the water at Stony Brook?
Currently 18.7 °C (updated continuously).
How warm is at Stony Brook in September?
In September, the water temperature recently averaged 21.9 °C.
When is the water warmest at Stony Brook?
Across the measurement record, August is on average the warmest month (24.1 °C).
