Driveability rear end sliding

I have a 2004 Saturn L300 Car has just been aligned, new tires but when on wet roads, wet but not heavy rain, the rear end wants to slide. Is it possible that the rear end is just to light? or could i be looking for something else? Thanks

If the rear end of the car has a tendency to slide on wet roads, the first two things to consider are:

The tires
The speed at which you are driving

First, check the inflation pressure of the tires. If they are more than 3 psi over the car manufacturer’s recommendations, then you need to adjust the pressure downward. Is it possible that some dufus has inflated them to the pressure listed on the sidewall, rather than using the pressure listed on the placard on the driver’s door jamb?

Since the tires are new, unless they are overinflated or are rated very low on resistance to hydroplaning, then the factor that would seem to have more importance would be the speed at which you are driving.