Hatch Charts

Detailed hatch emergence charts for 139 trout rivers across 11 western states including Montana, Colorado, Idaho, Wyoming, Oregon, California, and Utah, powered by Growing Degree Day analysis and 10 years of USGS water temperature data.

Select a river to see its full hatch chart with species timing, fly patterns, and GDD curves.
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About Our Data
GDD-Verified Multi-year GDD analysis with 5–11 years of USGS water temperature history. Highest confidence emergence predictions.
GDD-Supported GDD analysis with 3+ years of temperature data. Strong predictions backed by real water temp records.
Research-Based AI-researched hatch timing combined with initial GDD modeling. Predictions improve as more temperature data accumulates.

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See What's Hatching Now

Check the live hatch forecast for real-time emergence predictions across all 50 rivers.

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