Cold...

from sahih al bukhari:

Narrated Hudhaifa: The Prophet said about Ad-Dajjal that he would have water and fire with him: (what would seem to be) fire, would be cold water and (what would seem to be) water, would be fire. (Book #88, Hadith #244)

Narrated Nafi': Once on a very cold and stormy night, Ibn 'Umar pronounced the Adhan for the prayer and then said, "Pray in your homes." He (Ibn 'Umar) added. "On very cold and rainy nights Allah's Apostle used to order the Mu'adhdhin to say, 'Pray in your homes.' " (Book #11, Hadith #635)

Narrated Anas bin Malik: The Prophet used to offer the prayer earlier if it was very cold; and if it was very hot he used to delay the prayer, i.e. the Jumua prayer. (Book #13, Hadith #29)

Narrated Abu Wail: Abu Muisa said to'Abdullah bin Mas'ud, "If one does not find water (for ablution) can he give up the prayer?" Abdullah replied, "If you give the permission to perform Tayammum they will perform Tayammum even if water was available if one of them found it cold." Abu Musa said, "What about the statement of 'Ammar to 'Umar?" 'Abdullah replied, "Umar was not satisfied by his statement." (Book #7, Hadith #341)