Maryland · Brunswick, MD
Potomac River (Harpers Ferry) float season
Gauge 01638500 on the Harpers Ferry to Point of Rocks via Brunswick. Wide, island-dotted water below the Harpers Ferry confluence is the D.C. region's favorite big-river tubing and canoe-camping escape.
Right now at this gauge
loading CFS
Checking the live gauge…
Well above typical for this date
Live reading from the USGS gauge page for Potomac River (Harpers Ferry). Provisional data — subject to revision.
The year on this river
In a typical year at the Brunswick gauge, the Potomac River (Harpers Ferry) runs fullest Feb–Apr and leanest Aug–Oct. Where today's reading falls inside that rhythm matters more than the raw number — the same flow that feels thin in spring can be the summer norm. Half of all past March days at this gauge ran above 13,700 CFS; the September median is 2,180 CFS.
| Month | Typical flow (CFS) | Relative volume |
|---|---|---|
| January | 7,710 | |
| February | 9,250 | |
| March | 13,700 | |
| April | 11,900 | |
| May | 8,760 | |
| June | 5,085 | |
| July | 3,260 | |
| August | 2,740 | |
| September | 2,180 | |
| October | 2,260 | |
| November | 3,030 | |
| December | 5,850 |
Record context
This gauge has measured daily flow since 1895 — 131 years of record. The largest daily average ever logged here was 434,000 CFS, in March 1936. Rivers do that sometimes; it's why the safety panel above isn't decoration.
Planning dates? The trip-window checker shows what flows have historically looked like on any week you pick for this river, or see what a CFS actually looks like.
More Maryland float rivers
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Antietam Creek
Stone-bridge reach past Burnside Bridge near Sharpsburg
Fullest: Mar–May
-
Potomac River (Mather Gorge)
Great Falls and Mather Gorge above Little Falls
Fullest: Feb–Apr
-
Youghiogheny River (Upper)
Upper Yough, Sang Run to Friendsville
Fullest: Feb–Apr
Common questions
When is the Potomac River (Harpers Ferry) usually at its fullest?
At the Brunswick gauge, the fullest stretch of a typical year is Feb–Apr, with the single highest monthly median in March (about 13,700 CFS). The leanest months are usually Aug–Oct.
What is a typical summer flow on the Potomac River (Harpers Ferry)?
The July median at this gauge is about 3,260 CFS — half of past Julys ran higher, half lower. Late summer is this river's lean season, so expect readings to drift down as the season goes on.
Is the Potomac River (Harpers Ferry) safe to float right now?
No flow number can answer that, and this site never labels a river safe. What the data can tell you is how today's reading compares with 131 years of this date's history — well above typical means pushier, colder, faster water. Pair that context with a PFD, a look at the river from the bank, and a call to a local outfitter before you commit.
Which USGS gauge does this page use?
USGS gauge 01638500 (POTOMAC RIVER AT POINT OF ROCKS, MD), chosen because it best represents the Harpers Ferry to Point of Rocks via Brunswick. Daily records here reach back to 1895.
Data: USGS gauge 01638500, approved daily records 1895–2026, retrieved 2026-08-07. Live readings are provisional and subject to revision. U.S. Geological Survey data is public domain.