Sun River at Simms, MT
Missouri River & Headwaters (Montana) · USGS gauge 06085800 · Updated Oct 25, 11:23 AM PDT · USGS data, provisional
All 2 Sun River gauges in Montana
Reading time: Oct 25, 11:30 AM PDT · Provisional data
Flow is well above normal for the date. Water is likely fast and strong, wading is likely unsafe, and floating generally calls for experienced boaters. Check local reports and consider waiting.
- Vs. normal for this date
- 93rd percentile
- Typical range (25th–75th)
- 161–245 cfs
- Median for this date
- 197 cfs
- 7-day low / high
- 295 / 391 cfs
Water temperature & gage height
- Water temperature
- 5.1 °C (41 °F) as of Oct 25, 11:30 AM PDT · USGS 00010 · Provisional
- Gage height (stage)
- 2.86 ft as of Oct 25, 11:30 AM PDT · USGS 00065 · Provisional
Context only: these readings do not affect the status above, which is based on flow (cfs) alone. Gage height is the water level above this gauge's own reference point, not water depth, and can't be compared between gauges. Temperature converted from °C to °F by Flowcast. Source: USGS, provisional data.
Plain-language explanation
Sun River at Simms is flowing at 313 cubic feet per second (cfs) as of Oct 25, 11:30 AM PDT. That is among the highest flows on record for this time of year: higher than about 93% of the daily flows this gauge has recorded for this date (give or take 7 days) over 43 years of record (1966–2026).
The middle half of those historical flows runs from 161 to 245 cfs, with a median of 197 cfs; the lowest 10% of days are at or below 142 cfs and the highest 10% at or above 286 cfs.
Over the last 24 hours the flow has been falling (-10.8%). In the last 7 days it ranged from 295 to 391 cfs.
Why this status: Flow is above the seasonal 90th percentile and above the 60th percentile of all days on record.
Quick answers
Is the Sun River at Simms fishable today?
Flowcast's status for the Sun River at Simms is “Use caution”: flow is 313 cfs, well above normal for the date, at the 93rd percentile for this date (as of Oct 25, 11:30 AM PDT). That describes flow only. It says nothing about water clarity, temperature, fish activity, access or fishing regulations.
What is the current flow of the Sun River at Simms?
313 cubic feet per second at USGS gauge 06085800 as of Oct 25, 11:30 AM PDT, provisional data.
Is the Sun River at Simms too high or too low right now?
It is high: well above the typical range for the date (161 to 245 cfs).
Is the Sun River at Simms rising or falling?
Over the last 24 hours the flow has been falling (-10.8%).
What is a normal flow for the Sun River at Simms in October?
For this date (give or take 7 days) the median is 197 cfs and the middle half of days runs 161 to 245 cfs, over 43 years of USGS record.
7-day trend
Hourly flow in cfs, Pacific time. The shaded band is the typical range (25th–75th percentile) for this date, shown when it falls within the chart.
| Day (Pacific) | Mean cfs | Percentile | Status that day |
|---|---|---|---|
| Mon Oct 19 | 304 | 91st | Use caution |
| Tue Oct 20 | 299 | 90th | High but doable |
| Wed Oct 21 | 295 | 89th | High but doable |
| Thu Oct 22 | 298 | 90th | Use caution |
| Fri Oct 23 | 327 | 93rd | Use caution |
| Sat Oct 24 | 348 | 94th | Use caution |
| Sun Oct 25 (so far) | 320 | 93rd | Use caution |
Seasonal context
Shaded band: 10th–90th percentile of daily flows through the year; dashed line: median. Log scale. Dot: today's flow. Based on 43 years of USGS daily data (1966–2026).
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Official resources
- USGS site page for gauge 06085800 (USGS: live readings, history, station details)
- Montana fishing regulations (FWP)
- Montana aquatic invasive species (FWP)
- Montana waterbody restrictions and closures (FWP)
- Montana fishing access sites (FWP)
Agency notices that mention this river
- “Sun River: Emergency river closure due to bridge construction (closed to all forms of use) are in effect for the Sun River - beginning 500 feet upstream and ending 500 feet downstream of the Sun River Bridge (also know as Pishkun Road Bridge) starting June 1. Adoption of an emergency rule closing a portion of the Sun River (MAR Notice No. 2025-301.1). The closure of this portion of the Sun River is in place from June 1 to November 15, 2026.” (Montana FWP current waterbody restrictions)
Copied from the Montana FWP current waterbody restrictions page as of Oct 25, 2:11 PM PDT. They match on the river's name only and may concern a different stretch. Open the page for the details.
Links go to the agencies' own websites and were checked as working. Flowcast does not summarize fishing or boating rules: regulations and closures change, and the agency pages are the authority.
About this gauge
- USGS site
- USGS-06085800
- USGS name
- Sun River At Simms Mt
- Drainage area
- 1,296 sq mi
- Location
- 47.5016, -111.9319
- Record in this analysis
- 1966–2026
Nearby gauges
- Sun River near Vaughn, MT Use caution 571 cfs · about 20 mi away (straight line)
- Smith River near Eden, MT Fishable/Floatable 136 cfs · about 33 mi away (straight line)
- Missouri River below Holter Dam, near Wolf Creek, MT Too low 2,920 cfs · about 35 mi away (straight line)
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