Boston flood history
1,205 days with roads at risk since 1996
Record high water
15.16 ft
Jan 4, 2018 · 129 roads at risk
Days a year, then vs now
27 → 48
1996–2005 vs 2016–2025
Most recent
Sep 29, 2026
11.96 ft · 4 roads at risk
On the map
The biggest days
Jan 4, 2018: 129 roads at risk15.16 ft at the Boston gauge · 3.3 ft above the tide tables · deepest: Severe · model estimate
Estimates, not records of actual flooding. Each day is NOAA's verified high water at the tide gauge, run through FloodRoute's flood model on today's roads and elevations, in dry weather. Drains, levees, tide gates, rain, road changes and elevation error all mean real conditions differed. Not for property, real-estate, insurance, lending, engineering or legal decisions.
1996–2026
Days with roads at risk, by year
Since 1996
Highest water
| Date | High water · Boston | vs tide tables | Roads at risk | Deepest streets (model) |
|---|---|---|---|---|
| 15.16 ft | +3.33 ft | 129Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 14.63 ft | +3.25 ft | 115Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 14.41 ft | +2.99 ft | 112Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.97 ft | +2.33 ft | 90Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.91 ft | +2.68 ft | 81Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.83 ft | +1.84 ft | 70Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.83 ft | +3.21 ft | 70Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.80 ft | +1.90 ft | 70Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.78 ft | +2.38 ft | 70Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 13.70 ft | +3.59 ft | 66Severe | Chelsea Street, William T. Morrissey Boulevard, Marginal Street |
Latest verified
Most recent days
| Date | High water · Boston | vs tide tables | Roads at risk | Deepest streets (model) |
|---|---|---|---|---|
| 11.96 ft | +0.86 ft | 4Possible | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 12.45 ft | +1.53 ft | 8Likely | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 12.27 ft | +1.66 ft | 6Likely | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 12.16 ft | +0.85 ft | 5Possible | Chelsea Street, William T. Morrissey Boulevard, Marginal Street | |
| 12.29 ft | +0.90 ft | 6Likely | Chelsea Street, William T. Morrissey Boulevard, Marginal Street |
Every day, every year
Browse by year
About this data: method, sources and free downloads
Since 1996, NOAA's Boston tide gauge has recorded water high enough for FloodRoute's model to put at least one Boston road at risk on 1,205 days, about 39 a year. The highest water was 15.16 ft on Thursday, January 4, 2018, 3.33 ft above the tide tables; at that level the model estimates 129 Boston roads were at risk, including Chelsea Street, William T. Morrissey Boulevard and Marginal Street. Those days have become more common: about 27 a year in 1996–2005, versus 48 a year in 2016–2025.
For every day since 1996 we take NOAA's verified highest observed water at the tide gauge, adjust it to the town's prediction station exactly as the live forecast does (the gauge's departure from the tide tables, minus the departure already built into our calibration), and run FloodRoute's flood model on today's road network and street elevations. A day counts when at least one road in the town is at or below that water level by the model's rules. Rain is not included, so wet days were likely worse.
Gauge: NOAA 8443970 (Boston). Heights are feet above MLLW.
Free to use under the Open Database License (ODbL) 1.0. Credit: FloodRoute (floodroute.com), © OpenStreetMap contributors, NOAA CO-OPS. Please describe it as estimates, never as observed flooding.
Cite as: FloodRoute (2026). Boston, MA king tide flood history (model estimates). https://floodroute.com/ma/boston/history. Open Database License (ODbL) 1.0.
FAQ
Boston flood history: questions, answered
How often do roads flood at high tide in Boston?
By FloodRoute's estimate, at least one Boston road was at risk on 1,205 days between 1996 and Sep 30, 2026, about 39 a year. Those days have become more common: about 27 a year in 1996–2005, versus 48 a year in 2016–2025. Most of those days are shallow water on a few low streets; the biggest days put dozens of roads at risk.
What was the highest tide in Boston since 1996?
Thursday, January 4, 2018: NOAA's Boston tide gauge recorded 15.16 ft (MLLW), 3.33 ft above the tide tables. At that level FloodRoute's model estimates 129 Boston roads were at risk, including Chelsea Street, William T. Morrissey Boulevard and Marginal Street.
When did a high tide last put Boston roads at risk?
The most recent day in the verified record is Tuesday, September 29, 2026: 11.96 ft at the Boston gauge, 4 roads at risk. NOAA verifies data with a lag of a month or two; the live forecast covers today and the weeks ahead.
Is this a record of actual flooding in Boston?
No. Estimates, not records of actual flooding. Each day is NOAA's verified high water at the tide gauge, run through FloodRoute's flood model on today's roads and elevations, in dry weather. Drains, levees, tide gates, rain, road changes and elevation error all mean real conditions differed. Not for property, real-estate, insurance, lending, engineering or legal decisions. Neighbor flood reports in the FloodRoute app are the ground truth we use to check and improve the model.
Can I use this data?
Yes. Download it as CSV or JSON under the Open Database License (ODbL) 1.0, with attribution to FloodRoute (floodroute.com), © OpenStreetMap contributors, NOAA CO-OPS. Please describe it as estimates, never as observed flooding. More on the open data page.