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Where to fish

  • Forecast
  • Catches

Mine

  • Favorites
Forecast
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© 2026·AI-powered bite forecast
0.1.0+2161 · b4069346

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United Kingdom / Caerphilly County Borough / Rhymney River

Bite forecast: Rhymney River

  • length 42 km
  • Flows into Bristol Channel
Loading map…

Best fishing days for the next week

  1. TuesdaySeptember 8weather-based forecast
    52/100medium activity

    Cloudy: 12–17 °C

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Rhymney River (Caerphilly County Borough) — a spot well known among anglers. About 42 km long. Flows into Bristol Channel. Nearby towns: Rhymney, New Tredegar and Caerphilly. This page shows an hourly bite forecast for today and the week ahead; the algorithm factors in the weather, atmospheric pressure, and the moon phase.

Catches

Recorded 7 catches here. Most commonly caught: Brown trout, Grayling. Peak season: August–November.

  • Grayling
    Rhymney River
    15 °C4 mph
    Nov 13, 2022, 11:39 AM
  • Brown trout
    Rhymney River
    19 °C9 mph
    Sep 22, 2020, 1:20 PM
  • Grayling
    Rhymney River
    17 °C13 mph
    Aug 06, 2017, 2:21 PM
  • Grayling
    Wales
    17 °C13 mph
    Aug 06, 2017, 2:21 PM
  • Brown trout
    Rhymney River
    17 °C13 mph
    Aug 06, 2017, 12:35 PM
  • Brown trout
    Rhymney River
    16 °C9 mph
    Aug 05, 2017, 9:37 AM
  • Brown trout
    Rhymney River
    16 °C9 mph
    Aug 05, 2017, 8:44 AM
WednesdaySeptember 2weather-based forecast
51/100medium activity

Drizzle: 15–19 °C

  • ThursdaySeptember 3weather-based forecast
    51/100medium activity

    Cloudy: 17–20 °C

  • Nearby towns

    • Rhymney0.1 mi
    • New Tredegar0.1 mi
    • Caerphilly1 mi

    Bite calendar

    Wednesday, September 2

    Aug 31 – Sep 6
    Mon
    Tue
    Wed
    Thu
    Fri
    Sat
    Sun
    Bite activity:highmediumlowslow
    Based on:weatherseasonal
    What is a bite calendar?
    PikeBarbelDaceEuropean eelGraylingRuffeWhitefishZanderPerchAtlantic salmonBreamCarpRainbow troutBrown troutWels catfishIdeRoachChubCrucian carpBleakRuddTenchWhite bream

    Atlantic salmon

    6/10 · Fair

    Hourly activity

    0:006:0012:0018:0023:00
    Bite activity:highmediumlow

    The bite is strong — fish are active. A thunderstorm is possible: activity rises before the front and drops after.

    Peak bite hours

    Best time — 06:00–08:00 (dawn bite) and 20:00–21:00 (dusk bite).

    Tactics

    Work the cover — snags, weed edges, hole entrances; retrieve the lure with pauses.

    Lures

    The water's turning murky — go with bright, noisy lures: salmon spoon or salmon fly.

    Gear

    No special gear needed — seasonal clothing will do. A thunderstorm is possible — bring a rain jacket, and pack up at the first rumble of thunder.

    Summary

    Worth going — it's a productive day.

    How this forecast is calculated

    Why this forecast

    The computed water temperature is around 16 °C — warmer than the 4–14 °C comfort range for Atlantic salmon: in the heat it drops deeper and feeds less often.

    Computed water temperature by month; the green band is the 4–14 °C comfort rangecomfort 4–14 °C16 °C
    JFMAMJJASOND

    Atlantic salmon works the twilight: the peaks are pinned to sunrise and sunset — their times are in the sun-and-moon card above.

    The day: daylight hours and when Atlantic salmon feeds0:0012:0024:00

    Pressure is dropping 3 hPa over the day — fish are usually more active ahead of a weather change.

    Pressure through the day, 3 hPa change
    00:00 · 102023:00 · 1017 hPa

    One more input — the moon's feeding windows: within their hours the score sits higher than across the rest of the day. The window times are in the “Solunar feeding periods” card below.

    Feeding windows on the day scale0:0012:0024:00

    September is an active season for Atlantic salmon here.

    JFMAMJJASOND

    These are the same values the bite curve above was computed from. How the forecast works

    2 SepWednesday, September 2
    +17°

    Drizzle · feels like +16°

    Low / high
    +14°…+19°
    Precipitation
    0.5 mm
    Wind
    14 mph SW
    Cloud cover
    100%
    Humidity
    96%
    Pressure
    1017 hPa
    00:00+15°0.2 mm6 mphsouth wind, 6 mph96%100%
    01:00+15°2.1 mm6 mphsouthwest wind, 6 mph98%100%
    02:00+14°0.7 mm2 mphsouth wind, 2 mph98%100%
    03:00+15°4.7 mm2 mphsouth wind, 2 mph99%100%
    04:00+15°0.7 mm4 mphsouthwest wind, 4 mph97%100%
    05:00+15°0.1 mm6 mphsouthwest wind, 6 mph96%95%
    06:00+15°—6 mphsouth wind, 6 mph97%95%
    07:00+15°—6 mphsouth wind, 6 mph96%98%
    08:00+15°—5 mphsouth wind, 5 mph95%100%
    09:00+15°0.2 mm9 mphsouth wind, 9 mph95%100%
    10:00+15°0.6 mm10 mphsouth wind, 10 mph97%100%
    11:00+16°1.0 mm12 mphsouthwest wind, 12 mph96%100%
    12:00+17°0.5 mm14 mphsouthwest wind, 14 mph96%100%
    13:00+18°0.6 mm15 mphsouthwest wind, 15 mph94%99%
    14:00+19°0.1 mm16 mphsouthwest wind, 16 mph89%91%
    15:00+18°0.5 mm12 mphsouthwest wind, 12 mph94%100%
    16:00+18°0.8 mm16 mphsouthwest wind, 16 mph96%100%
    17:00+18°0.5 mm11 mphwest wind, 11 mph93%81%
    18:00+18°0.3 mm12 mphsouthwest wind, 12 mph94%93%
    19:00+17°0.3 mm11 mphwest wind, 11 mph94%98%
    20:00+17°—10 mphsouthwest wind, 10 mph93%96%
    21:00+17°0.1 mm9 mphwest wind, 9 mph93%99%
    22:00+17°0.2 mm10 mphsouthwest wind, 10 mph96%100%
    23:00+17°—7 mphsouthwest wind, 7 mph97%100%
    +19°+17°+14°
    Weather throughout the day
    0:006:0012:0018:0023:00

    Sun and moon

    Wednesday, September 2
    The day: daylight and the hours the moon is above the horizon. Local time0:0012:0024:00
    DaylightMoon above the horizon
    Sunrise
    06:26
    Sunset
    19:57
    Day length
    13 h 31 min
    Sunshine hours
    0 min
    UV index
    2
    low
    Moon
    Waning gibbous
    Moonrise
    21:21
    Moonset
    13:14

    The day is 4 min shorter than yesterday.

    Sunshine hours count direct sun only — cloud cover cuts it, so it is shorter than daylight.

    Solunar feeding periods

    +13% in the windowWednesday, September 2
    Feeding windows on the day scale, local time0:0012:0024:00
    Major periodsMinor periods
    • Major03:56–05:56Moon overhead
    • Minor12:44–13:44Moonset
    • Major16:23–18:23Moon underfoot
    • Minor20:51–21:51Moonrise

    The windows are set by the moon's transit and rise, and the forecast above already accounts for them: within these hours the bite score sits higher than across the rest of the day, while the day's overall level still comes from the catch-calibrated model.

    What are solunar periods?

    BiteGuide·From anglers’ reports

    What actually worked on this water

    Based on 7 verified catchesPeriod: 2017–2022

    This is a summary of anglers' reports, not a proven cause of the bite: conditions lining up does not mean they drove it.

    By fish species

    vertical axis — number of catches

    024
    43
    Brown troutGrayling
    By fish species
    ValueCatchesShare
    Brown trout457%
    Grayling343%

    By month

    vertical axis — number of catches

    035
    511
    AugSepNov
    By month
    ValueCatchesShare
    Aug571%
    Sep114%
    Nov114%

    By time of day

    vertical axis — number of catches

    012
    111112
    91011131415
    By time of day
    ValueCatchesShare
    09:00114%
    10:00114%
    11:00114%
    13:00114%
    14:00114%
    15:00229%

    Pressure, mmHg

    vertical axis — number of catches

    023
    133
    750755760
    Pressure, mmHg
    ValueCatchesShare
    750–754 mmHg114%
    755–759 mmHg343%
    760–764 mmHg343%

    Wind direction

    vertical axis — number of catches

    035
    115
    ESWW
    Wind direction
    ValueCatchesShare
    E114%
    SW114%
    W571%

    Wind speed, mph

    vertical axis — number of catches

    023
    133
    4913
    Wind speed, mph
    ValueCatchesShare
    4–7 mph114%
    9–11 mph343%
    13–16 mph343%

    Nearby rivers

    • Sirhowy River3 mi
    • Rhymney River3 mi
    • Bargod Taf3 mi
    • Nant Bargoed Rhymni4 mi
    • Nant yr Aber4 mi
    • Nant Bargod Rhymni4 mi
    • River Taff4 mi
    • Ebbw River4 mi
    • Nant Clydach6 mi
    • Ebbw Fawr River6 mi

    Nearby water bodies

    • ReservoirNant-y-draenog Reservoir3 mi
    • LakeTaff Bargoed Lake4 mi
    • LakeOgilvie Lake6 mi
    • ReservoirPant-yr-Eos reservoir7 mi