Here's how troutfinder.guide ranks days and times — every factor, every rule, explained in plain English.
Trend matters more than the number itself. A falling barometer — even a small drop over 12 hours — often triggers trout to feed actively. Rising pressure, especially above 1020 hPa, pushes fish deeper and makes them harder to tempt.
Dawn and dusk are reliably the best two periods on stillwaters. The two hours after sunrise and the two hours around sunset consistently produce more takes. Bright midday sun, especially with clear skies, is the hardest window — fish go deep and switch off.
A light-to-moderate ripple (5–9 mph) is ideal: it oxygenates the surface, concentrates drifting invertebrates on the windward shore, and breaks up the fish's view from below. Flat calm makes fish cautious and presentation critical. Strong winds (over 20 mph) push fish onto cover but make casting a battle.
Water temperature drives fish metabolism — but we score from air temperature and season, which predicts where water is heading. The key thresholds for rainbow trout in UK stillwaters: below 5°C fish are slow and deep; 8–15°C is the feeding sweet spot; above 18°C fish seek depth and cooler water, reducing their catchability.
We track growing degree days (GDD) — the accumulated warmth above a base temperature since 1 January. Different insects emerge at predictable GDD thresholds: buzzers (chironomids) start early, damselflies in June, sedge evenings through summer. When a hatch window is active, it boosts both feeding and catchability scores.
Overcast skies are nearly always better than clear ones for stillwater trout. Cloud cover reduces UV penetration, keeping fish confident in shallower water and extending prime windows through the day. Broken cloud is good; bright blue sky (especially with high pressure) is the hardest condition.
We score every forecast hour between 6am and 9pm. Each factor contributes to two sub-scores: feeding activity (is the fish likely to be feeding?) and catchability(will it take a fly?). These combine into a single 0–100 score. We then find the best 3-hour window and call out the day's peak.
A score of 70+ means conditions are stacking up in your favour — pressure, light, wind, and season all pointing the same direction. Below 30 and something significant is working against you.
A freshly-stocked water fishes very differently. We don't currently have stocking dates — your logbook notes help fill this gap.
Heavy angling pressure, especially on smaller tarns, can switch fish off quickly. We don't know how many rods are on the water.
A sheltered bay can fish two hours longer into wind than the score suggests. The numbers are a starting point, not a substitute for reading the water.
Our hatch thresholds and scoring weights are calibrated on published entomology research, not seasons of catch records from these specific waters. They'll improve as the logbook builds.
A black-box score is useless to an angler. You need to understand whya score is high or low — because conditions change through the day, and knowing which factors are at play helps you decide where to fish, what to throw, and when to change tactic. We'd rather teach you to read a day than hand you a number and ask you to trust it.