Because of the profile, these tires seem to be less susceptible to hydroplane. Regardless, wet traction is reduced. Worn tires also lack the flexibility of a fresh set and are more prone to uncontrolled slip.
Cracking is not a sign of wear (how many miles it has), it has more to do with tire material and environmental conditions. Check out the 4 digit code on the sidewall to determine when the tire was manufactured. If this occurred on a tire less than a year old, I would be emailing the tire manufacturer. With that said, cracking is not really dangerous if it is superficial. If it goes in deep, which is kind of subjective, then I would be worried.
Take a grinder, grind in some deeper threads. " Just like New". But seriously your tires look really old, not super worn but old. If you ride nothing but the speed limit around town it'll probably be alright for another 2-3k i'll say. If you have to suddenly brake really fast, good luck with the grip. Ride it like your on a 50cc mo-ped if your broke and can't afford new tires.