Salmon Fishing Forecasts: The Conditions That Actually Move Salmon
Quick Answer
A salmon forecast is different from a general fish forecast, because salmon spend their lives crossing between two very different environments and the signal that matters flips depending on where in that journey they are. In salt water, the useful signals are sea-surface temperature and its fronts, bait concentration and current. In fresh water — once fish are running — the dominant signals are river flow and water temperature, and neither of them is visible in a marine forecast. This page explains which conditions to read at which stage, and where FishRadar's numbers help versus where you need a river gauge.
The three stages, and what to read in each
1. Salmon at sea (feeding). Chinook, coho and Atlantic salmon feeding offshore follow temperature and bait. What matters:
Sea-surface temperature and thermal fronts. Salmon hold along temperature boundaries rather than in uniform water. A front — a sharp change in temperature over a short distance — is a line to work along. FishRadar computes a front gradient in °C per kilometre for every scored coordinate.
Chlorophyll. It is a proxy for productivity: plankton, then bait, then salmon. Colour changes on the water often mark the same edges.
Mixed-layer depth. It tells you how deep the surface temperature reading remains true, which decides how deep to fish.
Current and shear. Moving water and the boundary between surface and deeper flow concentrate bait.
2. Salmon staging near the river mouth. This is the transition, and it is tide-driven where tides are significant. Fish hold in the estuary or just outside, waiting on flow. Incoming tide moving fresh water back and cool water in is the classic window; on tidal coasts the mid-tide flow periods are usually the productive hours.
3. Salmon in the river (running). Once fish enter fresh water, marine signals stop being the answer:
Flow (discharge) is the single most important variable. Salmon typically move on rising or recently-risen water — a rain event that lifts the river often starts a run within a day. Very low flow holds fish in pools and makes them hard to move; very high, coloured water can shut fishing down entirely.
Water temperature governs whether they will take. Roughly speaking, fishing slows sharply at the warm end (above about 18–20 °C, when oxygen falls and fish become stressed) and at the very cold end.
Water clarity, which follows flow with a lag: fish often take best on the clearing edge of a spate rather than at its peak.
Barometric pressure and light matter, but less than flow and temperature.
Where FishRadar helps, and where it does not
It helps at sea and in the estuary. For a coastal or offshore salmon spot, the score already reads sea-surface temperature and its anomaly, front gradient, chlorophyll, mixed-layer depth, wind, wave, current and — where the tidal range justifies it — tide phase. That is most of the marine picture.
In rivers it is honest about a gap. FishRadar reads USGS gauge data (discharge, gauge height, stage trend, water temperature) where a gauge is near a scored freshwater spot in the United States, and that is exactly the flow information a salmon angler wants. Outside the US, river gauge coverage is thin, and no forecast on this site should be read as a flow forecast where there is no gauge. For a river run outside gauge coverage, check the local water authority's own flow data. Saying so is more useful than pretending the number covers it.
It does not predict the run. Run timing depends on the year's stock, hatchery releases, ocean survival and river conditions upstream — none of which is a live sensor reading. Regional run forecasts published by fisheries agencies are the right source for "are the fish here yet". A conditions forecast answers "if they are here, is today a day they will move and take".
Practical reading
In salt water: look for a temperature edge rather than a temperature. Work the front, and set depth from the mixed-layer figure.
At the mouth: fish the moving water. On tidal coasts use the mid-tide windows; where tidal range is small, use the solunar peaks and light transitions instead.
In the river: watch the hydrograph before the weather. A rise after rain is the event to fish; the clearing edge afterwards is usually better than the peak.
Respect the temperature ceiling. Warm, low water is when catch-and-release mortality climbs steeply. Many jurisdictions close or restrict fishing on that basis — and where they do not, the fish still pay.
Check the rules for that specific water. Salmon are among the most tightly regulated species anywhere: seasons, gear restrictions, retention bans and stretch-by-stretch rules are normal. FishRadar publishes structured regulations where they have been verified, and names the authority.
Follow the conditions
Salmon spots and their live scores — Atlantic salmon, Chinook and coho: every scored location where each is among the tracked species.