"He must know something"

It was nine in the evening when Jonathan stepped out, and to his surprise, it was raining again in San Diego, a fine drizzle that left only the slightest sensation when it struck one's face.

Jonathan had always found the rain comforting, its rhythmic pattern a soothing lullaby for his weary mind.  But after living in Black Sea City for so long, he had developed an aversion to rainy days. That dreary metropolis saw so much rain, and the downpours brought only grim associations now. 

What if the mutated creatures' blood flowed further in the rain, would it infect more creatures?  Or would it only be potent at a certain concentration, losing its effect when diluted by the rain?