When does Chehalis River at Porter, WA normally run highest?

January, on the long-term record. The median daily flow that month is about 7,216.1 cfs, against 376.9 cfs in August, the lowest month. These are historical normals for the date, not a forecast and not today's reading.

What is a normal flow for Chehalis River at Porter, WA?

It depends on the month. In January, half of days historically fall near 7,216.1 cfs, with the middle 80% of days between 2,668.1 and 19,922.6 cfs. The month-by-month table on this page gives the full range.

How long has Chehalis River at Porter, WA been measured?

Discharge records at USGS site 12031000 begin in 1947, about 79 years, covering roughly 9,200 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.

Is there a flow forecast for Chehalis River at Porter, WA?

Yes. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on this basin's observed flows, weather, and snowpack, and issues a daily flow outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on the live gauge screen. Open live conditions to see the current outlook.

Where is Chehalis River at Porter, WA?

The gauge sits at 46.93926, -123.31432, in Washington, in hydrologic subbasin 17100103, at an elevation of about 38 feet, draining roughly 1,294 square miles.

Can I use Chehalis River at Porter, WA data for flood or safety decisions?

No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

USGS Streamgage 12031000

Chehalis River at Porter, WA

Chehalis River at Porter, WA is USGS streamgage 12031000 in Washington, monitoring river discharge in hydrologic subbasin 17100103. It sits on the Chehalis River, alongside 6 other gauges Rivermatics tracks on the same river. It drains a watershed of about 1,294 square miles. Discharge records at this site go back to 1947. Typical flow runs near 566.6 cfs in July and 3,683.7 cfs in April, with the higher of the two arriving in April. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead.

View live conditions & forecast →

Gauge details

State: Washington
Drainage area: 1,294 sq mi
Gauge elevation: 38 ft
Subbasin (HUC-8): 17100103
Coordinates: 46.93926, -123.31432
USGS site number: 12031000
Records begin: 1947-01-26 (79 years)
Rivermatics forecast: 14-day flow outlook

14-day flow forecast

Based on observations through September 10 for Chehalis River at Porter, WA. Each day carries a median estimate and the band the model expects the flow to fall within — not a single number to plan against. Forecasts are re-issued daily; see the live screen for the current outlook.

Forecast daily mean discharge in cubic feet per second, by date
Date	Low p10	Expected p50	High p90
September 11	336	348	360
September 12	328	347	375
September 13	344	383	483
September 14	364	445	625
September 15	362	441	603
September 16	350	418	553
September 17	334	393	511
September 18	322	375	478
September 19	312	360	448
September 20	306	353	430
September 21	299	344	417
September 22	289	334	404
September 23	284	328	394
September 24	279	324	389

All values in cubic feet per second (cfs). Estimates only — do not use them for navigation or for any safety, rescue, or emergency decision.

Typical flow by month

Long-term daily discharge percentiles from the USGS record (up to 74 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month	Low p10	Typical p50	High p90
January	2,668.1	7,216.1	19,922.6
February	2,779.3	5,969.3	16,500
March	2,560.6	5,239.7	12,905.8
April	2,014	3,683.7	8,255.7
May	1,106.5	1,849	3,890.6
June	671.3	1,036.6	2,151.3
July	393.7	566.6	885.6
August	264.4	376.9	568
September	272.1	407.6	897.1
October	347.6	737.4	2,862.2
November	904.3	3,779	12,941.3
December	2,323.5	6,364.2	19,561.3

All values in cubic feet per second (cfs).

Common questions

When does Chehalis River at Porter, WA normally run highest?: January, on the long-term record. The median daily flow that month is about 7,216.1 cfs, against 376.9 cfs in August, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
What is a normal flow for Chehalis River at Porter, WA?: It depends on the month. In January, half of days historically fall near 7,216.1 cfs, with the middle 80% of days between 2,668.1 and 19,922.6 cfs. The month-by-month table on this page gives the full range.
How long has Chehalis River at Porter, WA been measured?: Discharge records at USGS site 12031000 begin in 1947, about 79 years, covering roughly 9,200 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
Is there a flow forecast for Chehalis River at Porter, WA?: Yes. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on this basin's observed flows, weather, and snowpack, and issues a daily flow outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on the live gauge screen. Open live conditions to see the current outlook.
Where is Chehalis River at Porter, WA?: The gauge sits at 46.93926, -123.31432, in Washington, in hydrologic subbasin 17100103, at an elevation of about 38 feet, draining roughly 1,294 square miles.
Can I use Chehalis River at Porter, WA data for flood or safety decisions?: No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

Upstream and downstream on the Chehalis River

Every gauge Rivermatics tracks on this river, ordered by drainage area — upstream first. See the Chehalis River in full.

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Chehalis River at Porter, WA this page
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