I'm no expert but I think he can get by for a few days without UV. The heat is a bigger problem. I think many people in cold areas keep heat packs on hand for such emergencies. Are you able to get out of the house or are you stuck? If you can, go out and buy some heat packs. You could place them near the cage or wrap them in a towel and place in his cage. Also, some people have generators for emergency but that doesn't help you now.
I know many species can handle as low as 50 degrees at night but not sure if that's safe for several days. What species do you have and where are you located? For now maybe cover the cage with some blankets to keep any remaining heat in. I also read once of someone letting their chameleon hang out on them for warmth. Your body heat may be the warmest heat source right now. If you are able to get out you could go to a hotel, or friend, or family member's house with your cham. Also try searching the forums for "power outage". There might be some other creative ideas.
That's all I can think of. Hopefully others here will have some ideas. I wish you luck!