Is it legal to with hold rent after 10 days of no heat after hurricane sandy?

If you lived in the leased premises during that 10 day period then you will be obligated to pay some portion of your rent. If you choose to withold your rent in full, the landlord will more than likely start an eviction action. At that point you will have the right to have a habitability hearing and the Judge will determine whether you are entitled to a rent abatement (percentage discount for lack of vital services). However, please be aware that before allowing you to have the hearing, the Court will require you post into Court the full amount of the rent at issue. I suggest that you speak with an attorney to discuss your rights and defenses. Good luck.