Scoring method
An almanac rates the moon.
We rate the water.
Every day gets a grade from A+ to F, built from twelve weighted measurements taken at the water you actually fish. The moon is one of them. It is worth 1%.
A moon-phase almanac measures the other 96% not at all, and prints the same answer for every angler in the country.
What actually moves a grade
Weights come from peer-reviewed fisheries research, not from what anglers have always said. Nothing scores highly here on reputation alone.
There are two sets, because a trout stream and a tidal flat are not the same problem. Tides only exist on the coast, streamflow only exists inland. Everything else is measured in both, and water temperature leads in both.
| Factor | Weight |
|---|---|
| Water temp | Freshwater23%Saltwater22% |
| Wind | Freshwater12%Saltwater13% |
| Tides | Freshwater–Saltwater12% |
| Precipitation | Freshwater8%Saltwater8% |
| Streamflow | Freshwater8%Saltwater– |
| Pressure | Freshwater7%Saltwater7% |
| Air temp | Freshwater6%Saltwater6% |
| Cloud cover | Freshwater6%Saltwater6% |
| UV index | Freshwater5%Saltwater5% |
| Solunar | Freshwater3%Saltwater3% |
| Humidity | Freshwater3%Saltwater2% |
| Moon phase | Freshwater1%Saltwater1% |
The two rows in amber are everything a moon-phase almanac can measure. They come to 4% of the model in fresh water and 4% in salt. Raw weights total 82 freshwater and 85 coastal, because tides and streamflow swap out by location. Normalization brings the runtime sum to 100.
Seven things a printed table cannot tell you
Not because it is badly made. Because it is astronomy, and none of these are astronomical. Each one changes a grade on our side, sometimes by enough to call off the trip.
The lake is frozen
We track freezing-degree-days across the past week, with a thaw override. A calendar printed last autumn will still call it a best day.
A front arrives tomorrow
Pressure is read as a rate of change across six hours, so a falling barometer shows up before the weather does. A printed table has no barometer.
The front already passed
The bluebird day, and the one people misread most often: clear, calm, cold-feeling, beautiful, and slow. Once pressure has climbed 4 mb off its recent low we read the day as post-frontal, stop paying the credits a rising barometer would otherwise earn, and hold that reading for as long as the fish needs, which runs from 12 hours to 72 depending on the species. A calendar printed in advance cannot know a front came through, and the nicest-looking day of the week is often the one behind it.
The river is blown out
USGS discharge plus 48-hour rainfall separates a helpful post-rain bite from muddy water nobody should drive to.
The water is wrong for your fish
Water too warm for your species caps the whole grade, down to 35 at full confidence. The ceiling closes in gradually rather than all at once, because a fish one degree outside its comfort range is not in a different mood from one at the edge of it: it reaches 55 by 5°F past the limit and the full 35 by 10°F. Cold gets treated differently again, because it is different: a pike under the ice is still feeding, so for species with a winter fishery the cold ceiling only falls to 72. No lunar alignment overrides any of it.
Oxygen has crashed
Dissolved oxygen from the gauge, against per-species thresholds. Trout take a penalty below 9 mg/L, bass below 8, estuarine species below 6. Fish stop feeding well before they die.
And where you are
Every item above is local. That is the one thing a single national calendar can never be.
The theory behind the tables
John Alden Knight compiled 33 factors thought to influence daily fish behaviour, then discarded thirty of them. The three he kept were the sun, the moon and the tide.
Water temperature was not one of the three. A century of fisheries research has since put it first. The tables have not changed, because a table that measures nothing has nothing to update. It predates real-time river gauges, offshore buoys and satellite sea-surface temperature, and it works exactly as well without them.
Where the numbers come from
Public instrument networks, read live. No proprietary black box, and nothing hand-entered.
| Factor | Measured by |
|---|---|
| Water temp | USGS gauge, NOAA buoy, satellite SST |
| Wind | Open-Meteo |
| Tides | NOAA CO-OPS |
| Precipitation | Open-Meteo |
| Streamflow | USGS discharge |
| Pressure | Open-Meteo, read as 6h rate of change |
| Air temp | Open-Meteo |
| Cloud cover | Open-Meteo |
| UV index | Open-Meteo |
| Solunar | Computed astronomy |
| Humidity | Open-Meteo, via vapour pressure deficit |
| Moon phase | Computed astronomy |
Why the weights look like this
Every weight traces to published fisheries research. Where the evidence contradicts a popular angling belief, the evidence wins, even when that means scoring something lower than an angler expects.
Ambient temperature was the only significant positive predictor of trout catch rate, and lunar phase showed no significant effect. Moon phase carries 1%.
Barometric pressure shows null or weak direct effects on catch rate. Pressure carries 7%, and is read as a rate of change rather than a level.
Water temperature dominates insect emergence, not humidity. Humidity carries 3% in fresh water and 2% in salt.
Apparent wind-direction effects trace back to confounded weather patterns, so wind is scored on speed and consistency rather than compass heading.
Also drawn on: Stoner 2004, Vinson & Angradi 2014, Arlinghaus 2017. Moon-sign fishing, where water signs are supposed to be the best days, is folklore and carries no weight here. The zodiac sign is still displayed for readers who expect to see it, and contributes nothing to any grade.
What we will not claim
We publish national pages too, and they carry the same blind spot as anyone else’s. A country-wide calendar cannot know your water temperature. So our monthly almanac and weekly outlook publish a lunar rating, labelled as one, and they stop at B+. An A-grade day needs conditions only a real location can supply, and we will not print one without them.
The full A+ to F grade appears when you enter a location, and never before. Both kinds of calendar have limits. Only one of them tells you where they are.
See it applied to your water. Every factor above, graded for your spot.