my 50 years of riding experience taught me, that when it first starts raining and/or rains very little, "is when the road is most slick". after there is a heavy rain for a little while the street/road isn't as slick because it washes a lot of the slick film off of the roadway.
it is always wise to be more careful on any wet streets. reduce speed, take corners more slowly, no hard acceleration or hard braking, increase following distance and watch for hazards such as water filled pot holes or debris that may have washed onto the roadway.
I would also advise to take an advance drivers class as this will also teach you about counter steering, hazard recognition and avoidance as well as how to avoid target fixation (main cause of accidents on motorcycles.