91 Buick Cenury A/C cut out when hot
 

My Landlady has a 91 Buick Cenury she only drive it about 35 miles a week
it has a V6 eng runs good but it geting hot out now and the A/C been working good but on a hot day the A/C will cut out when the car is hot
the car not overheating sometime the temp light will also come after the car cool down the A/C is fine what can make the A/C cut out ?

Thanks the car blow ice cold air till the motor get hot then just blow warm air after the car sit and cool down it blow cold the car don't seem to be overheating