More than anything else, it's the weather that determines whether a trip will be successful or unsuccessful. Rain, temperature, and humidity work together: understanding how they interact is more useful than any "secret spot."
Rain: how much and how
It's not enough that it rains: it matters how. A slow, sustained rainfall that penetrates deep into the soil is much more effective than a violent downpour that flows on the surface and isn't absorbed. The soil must retain water to allow the mycelium to activate.
Temperature and thermal shock
The drop in temperature following rain is often the decisive trigger: a difference of a few degrees between the heat before and the cool after, especially at night, seems to "alert" the mycelium that it's time to fruit. Each species has its own thresholds: summer porcini tolerate higher temperatures, autumn porcini prefer cooler weather.
Humidity and wind
Soil moisture must be maintained high for several days: dry winds and intense sun can quickly nullify even heavy rainfall, drying out the surface layers of the soil where the mycelium is most active.
The Mushroom Weather Score
Mentally adding together rain, temperature, humidity, and wind is tricky every time. That's why MushScout summarizes them in a daily score from 0 to 100: a quick way to figure out, before you set off, whether conditions are dire or whether it's best to wait a few more days.
When it is NOT a good idea to go out
After periods of prolonged drought, with temperatures below freezing, or after days of dry winds that have dried out the recently watered soil, the chances of recovery are significantly reduced. In these cases, it's better to wait for the next rain rather than waste a trip.