USGS Streamgage 06085800
Sun River at Simms, MT
Sun River at Simms, MT is USGS streamgage 06085800 in Montana, monitoring river discharge in hydrologic subbasin 10030104. It sits on the Sun River, alongside 3 other gauges Rivermatics tracks on the same river. It drains a watershed of about 1,296 square miles. Discharge records at this site go back to 1964. Typical flow runs near 141.8 cfs in July and 209.9 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, alongside daily high and low water-temperature forecasts.
View live conditions & forecast →
Gauge details
- State
- Montana
- Drainage area
- 1,296 sq mi
- Gauge elevation
- 3,555 ft
- Subbasin (HUC-8)
- 10030104
- Coordinates
- 47.50163, -111.93191
- USGS site number
- 06085800
- Records begin
- 1964-06-09 (62 years)
- Rivermatics forecast
- 14-day flow outlook + water temperature
14-day flow forecast
Based on observations through for Sun River at Simms, MT. 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.
| Date | Low p10 | Expected p50 | High p90 | Range |
|---|---|---|---|---|
| 254 | 282 | 315 | ||
| 239 | 290 | 359 | ||
| 217 | 277 | 355 | ||
| 193 | 260 | 337 | ||
| 176 | 246 | 324 | ||
| 187 | 260 | 365 | ||
| 185 | 266 | 377 | ||
| 169 | 252 | 362 | ||
| 156 | 238 | 340 | ||
| 141 | 224 | 322 | ||
| 122 | 204 | 297 | ||
| 123 | 199 | 286 | ||
| 122 | 196 | 280 | ||
| 119 | 189 | 272 |
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 60 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.
| Month | Low p10 | Typical p50 | High p90 | Range |
|---|---|---|---|---|
| January | 109.3 | 183.8 | 315.2 | |
| February | 108.6 | 195.6 | 304.3 | |
| March | 108.7 | 186.1 | 392.9 | |
| April | 91.5 | 209.9 | 675.3 | |
| May | 81.2 | 781.6 | 2,855.5 | |
| June | 113.7 | 1,152.8 | 4,591.7 | |
| July | 55.1 | 141.8 | 887.3 | |
| August | 52.8 | 125.9 | 284.5 | |
| September | 59.6 | 130.6 | 235.6 | |
| October | 117.8 | 186.4 | 298.9 | |
| November | 131.8 | 199.2 | 342.4 | |
| December | 97.4 | 179 | 312.9 |
All values in cubic feet per second (cfs).
Common questions
- When does Sun River at Simms, MT normally run highest?
- June, on the long-term record. The median daily flow that month is about 1,152.8 cfs, against 125.9 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 Sun River at Simms, MT?
- It depends on the month. In January, half of days historically fall near 183.8 cfs, with the middle 80% of days between 109.3 and 315.2 cfs. The month-by-month table on this page gives the full range.
- How long has Sun River at Simms, MT been measured?
- Discharge records at USGS site 06085800 begin in 1964, about 62 years, covering roughly 8,743 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
- Is there a flow forecast for Sun River at Simms, MT?
- 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. A companion model forecasts each day's water-temperature high and low. 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 Sun River at Simms, MT?
- The gauge sits at 47.50163, -111.93191, in Montana, in hydrologic subbasin 10030104, at an elevation of about 3,555 feet, draining roughly 1,296 square miles.
- Can I use Sun River at Simms, MT 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 Sun River
Every gauge Rivermatics tracks on this river, ordered by drainage area — upstream first. See the Sun River in full.
- Sun River below Diversion Dam near Augusta, MT 610 sq mi
- Sun River below Willow Creek near Augusta, MT 814 sq mi
- Sun River at Simms, MT this page
- Sun River near Vaughn, MT 1,774 sq mi