Heat or out at night

Question
No, he's no longer allowed in the house.  Two litter boxes didn't help, nothing did, so we put up baby gates to keep him off all the carpet.  When I found him in the middle of the Kitchen table that was it.  You have to understand that he was a very well trained cat until my daughter left home.  So he lives on the porch all the time, he's not allowed in the house.  We started letting him off the porch in the day time so he can find a cool place to sleep, usually under the bushes next to the house.  So he either has to stay on the porch the whole time we're gone or we leave the door so he can get out during the day which means he'll be able to get out at night too.  

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Followup To
Question -
Hi, we have a 14 year old, long haired male cat that has been declawed and neutered.  He was an indoor cat for over 13 years until my daughter went to college and nothing we did would convince him to use the litter box.  So we moved him outside onto our big screened in porch.  We prop a door open during the day and he goes outside and usually stays right around the house.  We give him a treat of canned food to entice him inside every evening about 6pm and then we close the door so he's not out at night.  Now here's my problem.  We live in the deep south and even though the porch is big and screened the temperature is often close to 100 out there during the day.  We are going to have to leave him for a week.  Which is the most dangerous for him, being on the porch all the time when the temperature gets that hot or us leaving the door open so he can go out night and day.  He has an automatic feeder and one for water so that's not a problem.  There are no neighbors or anyone who can put him in at night.

Thanks for any insight you an give me.
Answer -
well i would say for HIM the safest thing is to be in the house with no outside access, as long as you leave the air conditioning on for him.you say he goes out on the screened in porch but stays close to the house, im confused...sounds like he is getting off the porch into the yard. you do not want a declawed cat on his own out in the yard for a week. make sure you clean the potty before you go, you might even want to buy another litter box for him, maybe he just needs two boxes in the house. he will be fine in the house as long as he has food, water , liter box and air conditioning.
happy vacation!

Answer
well its still safest for him, to not be able to get out in the yard while you are gone, still safer for him to be totally confined to the house. you may also consider taking him, his food, and a liter box with you if you can. some cats LOVE to travel.