Rain can restore soil moisture and reduce drying, which may support fungal fruiting. It does not switch mushrooms on by itself: temperature, previous drought, habitat and species all affect what happens next.
Rain does not reach every forest floor equally
A millimetre describes how much water fell, not what it did below the canopy. A short shower may wet leaves and needles without recharging dry ground, while steady rain can penetrate further. Canopy cover, slope and drainage determine how much water remains available.
Mycelium is not the mushroom you see
The fungal network lives in soil, wood or in association with roots. The visible mushroom is a temporary fruiting body. A species may therefore inhabit a forest even when no mushrooms are visible during a visit.
Read a weather sequence, not a single shower
For a trip in Switzerland, consider accumulated rain, temperature, wind and the dryness of the preceding weeks together. Elevation and aspect matter too, since nearby slopes can retain very different amounts of moisture.
FAQ
Frequently asked questions
Is one heavy shower enough?
Not always. On very dry ground, water may run off or evaporate before it produces lasting moisture in the relevant soil layers.
Should I forage while it is raining?
Today's rain says little about what is already fruiting. The preceding weather, habitat and season are more informative than conditions at departure time.