We've done a few wet-weather tire tests in the past, and you can read them at the links below.
Splish Splash: Three grippy street tires tested in the rain.
Wet Tire Test: Continental vs. Michelin on a McLaren MP4-12C
In addition, Tire Rack always includes wet performance in their standard testing array, and their most recent applicable tests are these:
Extreme Performance Summer 2017
