Banks: two forks, one number
The Payette you see on this page is the main stem, and the gauge that measures it, USGS 13247500 near Horseshoe Bend, sits below the point where the North Fork and the South Fork come together at Banks. Idaho Fish and Game's own reach names show the join: the North Fork's lowest listed reach runs from Banks up to Smiths Ferry Bridge, and the main river is measured from Banks down. Everything upstream on both forks is added together by the time it reaches Horseshoe Bend.
That makes this gauge the right number for the main river and the wrong number for either fork. If you are fishing the North Fork, USGS has gauges at Banks, Cascade and McCall; for the South Fork, use the Lowman gauge. Fish and Game breaks the North Fork below Cascade Reservoir into its own named reaches, Cabarton Bridge to the reservoir, Smiths Ferry Bridge to Cabarton Bridge, and Banks to Smiths Ferry Bridge, and the Cabarton stretch is also an 11-mile Class II to III raft run, so the same crowding question applies up there. Fish and Game's planner describes the main Payette as 75 miles long, running from Boise County down to Payette County, with a tremendously diverse fishery, many access points, and floating from small craft a popular way to fish it.
Why summer reads high at Horseshoe Bend
Do not read a July number here the way you would on a freestone. The Horseshoe Bend record, which goes back to 1906, shows median monthly flows of about 7,600 cfs in May and 7,400 in June, as you would expect from snowmelt, but July and August stay high too, around 3,600 and 3,100 cfs. Only in September does the median drop to about 1,800, and from October through January it sits between roughly 1,050 and 1,160 cfs.
No shop publishes a wading range for this gauge, so the 1,000 to 2,000 cfs band used here is that record's September through March range, the months when the main river is lowest and most wadeable. Above it, plan on fishing from a boat or from the edges.
Each fork has its own rulebook
The main Payette has no special rules of its own, so Idaho's 2025 to 2027 Southwest Region general rules apply: open all year, six trout, six bass with none under 12 inches, and bull trout released. The forks are where it changes. On the South Fork and its tributaries, except the Middle Fork Payette drainage, the trout limit is two. On the North Fork, the stretch from Smylie Bridge at Hartsell to Payette Lake is catch and release for trout from December 1 to the Friday of Memorial Day weekend, and above Payette Lake, including its tributaries, kokanee are catch and release. The rest of the North Fork falls back to the general rules.
Salmon and steelhead fishing are closed unless Fish and Game opens a specific season, and the Southwest Region's steelhead definition, rainbows over 20 inches, applies only in waters the brochure names, so check it before assuming a big rainbow is either legal or off limits.
Redbands at one end, bass at the other
Fish and Game's species list for the main river reads like two fisheries stacked together: redband and rainbow trout and mountain whitefish, alongside smallmouth and largemouth bass, catfish, bullhead, crappie and bluegill. The planner ties that list to the whole 75 miles, which run past three USGS gauges at Horseshoe Bend, Emmett and Letha, so which fish you meet depends a lot on where along the river you start.
Share the upper main stem with boats. Cascade Raft and Kayak, which operates from a base overlooking the Main Payette about 45 minutes from Boise, runs an eight-mile Class II to III family trip on it, and the South Fork above carries Class III to IV commercial trips. Commercial trips run in the warm months, so expect company on the upper main stem in summer and plan fishing days around it.
Borrowing a Boise-area hatch chart
No shop publishes a Payette-specific hatch chart. The table borrows RiverReports' chart for the South Fork Boise, a Boise-area tailwater with a published chart: midges all year, blue-winged olives from fall through spring with hatches as early as February, PMDs and caddis through summer, and golden stones in June and July. Treat it as a starting point, and keep a few crayfish and minnow patterns in the box if you are fishing far enough down to meet the bass.