Best Fishing Times by ZIP: Solunar Calculator

Enter a ZIP code and a date and this page gives you the hours a fish is most likely to eat, calculated from where the sun actually sits in the sky at your location. It also computes your solunar major and minor periods to the minute — and then tells you honestly that it left them out of the score, because the only peer-reviewed head-to-head test of commercial solunar tables found they do not predict catch.

How these best fishing times are calculated

The index is built from one measured effect, and only that effect. In laboratory trials reported by Michels and colleagues in Environmental Biology of Fishes (2025), walleye prey-capture success averaged 20.5% in the narrow twilight light band running from nautical twilight to roughly three degrees below the horizon (0.05 to 1 lux), and fell to 10 to 12% both in brighter light and in full darkness. That is roughly a 1.9-fold advantage confined to a band that lasts, on average across our ten test cities, 102 minutes a day split between morning and evening.

So the tool computes exactly that band and scores against it. The plain-text formula:

prime band = the clock times when the sun sits between 12 degrees and 3 degrees below the horizon (morning and evening)
inside a prime band: index = 100
outside: index = max(54, 100 * exp(-(d * d) / (2 * 45 * 45)))
where d = minutes to the nearest edge of the nearest prime band

Two constants deserve to be defended rather than buried. The floor of 54 is not arbitrary: 100 divided by 54 gives 1.85, which reproduces the measured 20.5-versus-11 percent capture ratio, so the tool never claims a bigger day-night swing than the study measured. The 45-minute shoulder is a smoothing choice, not a measured value — it exists so the index does not fall off a cliff the second the sun clears three degrees, and we disclose it here so you can judge it. Nothing else enters the score. No moon phase, no moon position, no barometric pressure.

Worked example, done by hand

Kansas City, Missouri — ZIP 64108, which resolves to the 641 prefix centroid at 39.14 N, 94.57 W — on 15 September 2026, UTC offset -5. Type those inputs into the tool above and you will get these numbers back:

• Nautical dawn (sun at -12 degrees): 6:01 a.m.  →  prime band ends (sun at -3 degrees): 6:48 a.m.
• Sunrise 7:00 a.m., sunset 7:26 p.m.
• Evening prime band (sun at -3 degrees): 7:38 p.m.  →  nautical dusk (-12 degrees): 8:25 p.m. — 94 minutes of prime light across the two bands.
• Applying the formula, the index holds at or above 90 from 5:40 to 7:10 a.m. and from 7:20 to 8:50 p.m. Those are the day’s two windows: each prime band plus the shoulder either side of it.
• The same day’s solunar majors fall at 4:20 a.m. (moon underfoot) and 4:44 p.m. (moon overhead). Neither one touches either prime band. A solunar app would have sent you out at a quarter to five in the afternoon.

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Solunar periods: computed exactly, deliberately unscored

The tool still calculates your major periods (the two hours centered on the moon’s upper and lower transit) and minor periods (the hour centered on moonrise and moonset), to the minute, because people want to see them. They are displayed in their own panel, in purple, outside the index. Here is why.

Read that table as a whole and the honest summary is this. Lunar periodicity in fish is real but species-specific, directionally inconsistent, and small where anyone has quantified it. What does not survive contact with data is the specific claim solunar tables make: that the moon’s position sets a predictable best hour of the day, the same way, for every species, everywhere. That claim has been tested twice and failed twice, most recently against seven commercial services at once.

Where solunar tables came from

John Alden Knight published the solunar theory in The Modern Angler: Including the Solunar Theory (Charles Scribner’s Sons, 1936). He proposed two major daily peaks, when the moon is directly overhead and directly underfoot, and two minor peaks around moonrise and moonset, reasoning by analogy to marine tides — that inland waters experience something like a tide. It was a synthesis of angling folklore and lunar geometry, not a finding derived from fish-activity data. We deliberately do not repeat the widely circulated claims that Knight originated the idea in 1926 or that he screened “33 factors”; we could not trace either to a primary source, so we leave them out.

What actually predicts whether fish eat

Dawn and dusk are not interchangeable

Accelerometer tags on 37 fish in Toronto Harbour over two years found that largemouth bass acceleration peaked at dawn (0.521 plus or minus 0.012 m/s squared) and declined through the day, while northern pike peaked at dusk (0.212) ahead of dawn (0.178), both species lowest during the middle of the day and at night (Hlina et al., Animal Biotelemetry, 2026). The index treats the two twilights symmetrically because we have a published dawn-versus-dusk ratio for pike and not for bass, and we would rather flag the asymmetry than invent a number for it. Pick a species above and the tool tells you which twilight the literature favours.

Water temperature reference table

Every figure below is quoted from a state wildlife agency, a federal agency, or a university extension publication, with the source named. Blank cells are blank on purpose: we could not find the value in a source that meets that bar, and we would rather show you the gap than fill it with a number from a blog.

† These four optimum figures come from a US Nuclear Regulatory Commission environmental report, which is a federal agency document, but it attributes them to an internal reference we could not resolve. Treat them as indicative, not authoritative. ‡ Wisconsin DNR publishes a preferred range of 65 to 75 °F for brown trout, which sits above Nevada DEP’s optimum-growth range and above its own chronic threshold. Both cannot be right; we show the laboratory-derived figure and flag the conflict rather than pick silently. Our next data pass targets Great Lakes Fishery Commission Special Publication 87-3 (Wismer and Christie, 1987), which should close most of the blank cells above.

The solunar-versus-light dataset

The headline figure at the top of this page is computed, not asserted, and you can check it. For each of ten US cities we generated every day of 2027, computed the moon’s upper and lower transit, drew a two-hour major period around each, computed the prime light band from solar altitude, and tested for overlap. Minor periods use a one-hour window around moonrise and moonset.

The remarkable thing is how flat that column is. From Orlando to Bangor, across sixteen degrees of latitude, the agreement rate never leaves the 22.6 to 24.3 percent band — because the two systems are keyed to different clocks entirely. Solar twilight is locked to the solar day; lunar transit drifts about fifty minutes later every day. They coincide at roughly the rate chance predicts, which is the whole point.

How to read your best fishing times

• An index of 100 means the sun is inside the measured prime band. That is the strongest claim this tool makes, and it is about light, not about fish being hungry on command.
• The floor of 54 is not “bad fishing.” It is the middle of the day and the middle of the night, where the laboratory data put capture success at 10 to 12 percent instead of 20.5. Plenty of fish are caught at noon.
• Water temperature outranks everything on this page. If the water is 48 degrees and you are chasing largemouth bass, the prettiest twilight in the world will not fix it. Enter a temperature and read that panel first.
• The purple solunar panel is provided, not endorsed. If your major period happens to land inside a prime band, the tool says so — that happens about 23.5% of the time, and on those days the two systems agree by coincidence rather than by mechanism.
• This is a light and timing tool, not a fishing report. It knows nothing about your water, your bait, recent stocking, flow, or whether anyone has caught anything there since March.

Frequently asked questions

Sources

• Quigley, C.N., Gonzalez Murcia, J.D. and Kauwe, J.S.K. (2023). Popular solunar tables fail to predict fishing success in North American recreational freshwater trout fisheries. SN Applied Sciences 5:161.
• Hanson, K.C. et al. (2008). Effects of lunar cycles on the activity patterns and depth use of a temperate sport fish, the largemouth bass. Fisheries Management and Ecology 15:357-364.
• Vinson, M.R. and Angradi, T.R. (2014). Muskie lunacy: does the lunar cycle influence angler catch of muskellunge? PLOS ONE 9:e98046.
• Stevenson, B.C. and Millar, R.B. (2013). Promising the moon? Environmental and Ecological Statistics 20:591-608.
• Pulver, J.R. (2017). Does the lunar cycle affect reef fish catch rates? North American Journal of Fisheries Management 37:536-549.
• Poisson, F. et al. (2010). Effects of lunar cycle and fishing operations on longline-caught pelagic fish. Fishery Bulletin 108:268-281.
• Andrzejaczek, S. et al. (2025). Lunar cycle effects on pelagic predators and fisheries. Reviews in Fish Biology and Fisheries 35:77-94.
• Michels, N.O. et al. (2025). Visual sensitivity, foraging behavior, and success of walleye under ecologically relevant downwelling light conditions. Environmental Biology of Fishes 108:147-160.
• Hlina, B.L. et al. (2026). Seasonal effects on the acceleration of largemouth bass and northern pike in Toronto harbour. Animal Biotelemetry 14:5.
• Maule, A.G. and Horton, H.F. (1984). Feeding ecology of walleye in the mid-Columbia River. Fishery Bulletin 82:411-418.
• Knight, J.A. (1936). The Modern Angler: Including the Solunar Theory. Charles Scribner’s Sons.
• Wellborn, T.L. (1988). Channel catfish: life history and biology. SRAC Publication 180, Southern Regional Aquaculture Center.
• Nevada Division of Environmental Protection thermal tolerance analyses for rainbow (2015), brown (2017) and brook trout (2017).
• NOAA. Striped bass (Morone saxatilis) literature review on environmental influences on stock dynamics.
• Louisiana Coastal Protection and Restoration Authority, Largemouth Bass Habitat Suitability Index, 2016 revision.
• State agency species pages: Wisconsin DNR, Minnesota DNR, Iowa DNR, Virginia DWR, Oklahoma Department of Wildlife Conservation, Maine IFW, US National Park Service.
• US Naval Observatory Astronomical Applications Department, rise/set/transit/twilight data, used for engine validation.
• US Census Bureau 2024 ZCTA Gazetteer and 2020 ZCTA-to-county relationship file, used for ZIP prefix centroids.

Data updated August 2026. Sun and moon mathematics never stale. The species temperature table and the evidence review are re-checked annually each August, or sooner if a new controlled test of solunar tables is published. Known gaps are listed openly in the temperature table above.

Related on Popular Outdoorsman

This page is authoritative on when to fish: the sun, moon and water-temperature windows for one day in one place. It does not tell you how to fish them. For the late-spring window this table keeps pointing at, see post-spawn walleye and smallmouth in late May. For reaching a prime-light window quietly, see the 2026 fishing kayak rankings. Before you fish a cold-water window, read winter fishing safety: a good solunar window is never a reason to be on bad ice.