If the wet weather ends and you gently pull the infected blossom away, the young squash fruit may be worth saving if its blossom end has not darkened with rot. Prune off shriveled fruits attached to infected blossoms.
Grow squash at wide spacing, so that the leaves of neighboring plants barely overlap. After the soil has warmed in summer, mulch beneath plants to create a barrier between the soil and the plants' foliage. After the plants begin blooming, use soaker hoses instead of sprinklers to water thirsty plants.
Harvest affected fruits when they are small, because wet weather can cause the blossom end of the fruit to start rotting. Clear away weeds and tattered leaves that may slow the drying of squash blossoms after summer rains.