There is no reliable number of days that applies to every species and forest. Temperature, existing moisture, elevation and development stage can make fruiting bodies appear sooner, much later or not at all.
Why fixed calendars fail
The same rainfall behaves differently on a hot Swiss Plateau in July, in the Jura in September or at elevation after a cold night. Species develop at different rates, and rain may arrive too late after a deep drought.
Signals worth combining
Consider rainfall accumulated over several days, minimum and maximum temperatures, wind, ground moisture and the earlier weather. A shaded stand on deep soil may remain moist much longer than an exposed forest edge.
Plan without turning a clue into certainty
Treat time since rain as one clue among several. Compare elevations and habitats, and expect that a promising area can still be empty. That uncertainty is part of fungal ecology.
FAQ
Frequently asked questions
Is the seven to ten day rule reliable?
No. It may occasionally match a local observation, but it ignores species, soil, temperature, elevation and previous moisture.
Is recent rain better than a longer damp period?
Not necessarily. Sustained moisture may matter more than one isolated shower, especially after severe dryness.