Michigan · Grayling, MI

Au Sable River float season

Gauge 04136000 on the Grayling to Mio canoe corridor. Michigan's canoe-marathon river, where quick clear current slides past cedar sweepers, river camps, and the trout lore of the Holy Waters.

canoekayaktubing Fullest: Mar–May Leanest: Jul–Sep
Au Sable River — typical flow through the year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 150 500 1k 2k
median flow for the date middle half of years (25th–75th percentile) most years (10th–90th)

Right now at this gauge

loading CFS

Checking the live gauge…

Live reading from the USGS gauge page for Au Sable River. Provisional data — subject to revision.

The year on this river

In a typical year at the Grayling gauge, the Au Sable River runs fullest Mar–May and leanest Jul–Sep. 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 April days at this gauge ran above 1,190 CFS; the August median is 616 CFS.

Median of daily flows in each month across this gauge's full record — half of past days ran above these figures, half below.
Month Typical flow (CFS)
January 728
February 729
March 861
April 1,190
May 992
June 780
July 677
August 616
September 634
October 686
November 778
December 768

Record context

This gauge has measured daily flow since 1909 — 117 years of record. The largest daily average ever logged here was 3,220 CFS, in April 1998. 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 Michigan float rivers

Common questions

When is the Au Sable River usually at its fullest?

At the Grayling gauge, the fullest stretch of a typical year is Mar–May, with the single highest monthly median in April (about 1,190 CFS). The leanest months are usually Jul–Sep.

What is a typical summer flow on the Au Sable River?

The July median at this gauge is about 677 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 Au Sable River 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 36 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 04136000 (AU SABLE RIVER NEAR RED OAK, MI), chosen because it best represents the Grayling to Mio canoe corridor. Daily records here reach back to 1909.

Data: USGS gauge 04136000, approved daily records 1909–2026, retrieved 2026-08-07. Live readings are provisional and subject to revision. U.S. Geological Survey data is public domain.