A statistical analysis was performed on a sample of 4 days sequences in which rainfall occurred during the second day, in order to establish airborne pollen–precipitation relationships. Drizzle (precipitation ≤ 1 mm) and rain (precipitation > 1 mm) events were considered as well as arboreal or non-arboreal pollen. Results showed that arboreal pollen decreases synchronically with the occurrence of a drizzle, registering the minimum value the following day of the precipitation occurrence. The high frequencies of fog and wet soil associated with the following day of drizzle occurrence support the hypothesis that besides the wash out, airborne pollen concentration could decrease by nucleation and impaction processes. As well, diurnal variation suggests that high humidity conditions could also affect pollen emission as already demonstrated by other authors.