But the day of the Lord will come like a thief.
The heavens will disappear with a roar;
the elements will be destroyed by fire,
and the earth and everything in it will be laid bare.  

2 Peter 3:10
(from New International Version)

Brothers, we do not want you to be ignorant about those who fall asleep, or to grieve like the rest of men, who have no hope. We believe that Jesus died and rose again and so we believe that God will bring with Jesus those who have fallen asleep in him. According to the Lord's own word, we tell you that we who are still alive, who are left till the coming of the Lord, willcertainly not precede those who have fallen asleep. For the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first. After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever. Therefore encourage each other with these words. Now, brothers, about times and dates we do not need to write to you,  for you know very well that the day of the Lord will come like a thief in the night. While people are saying, "Peace and safety," destruction will come on them suddenly, as labor pains on a pregnant woman, and they will not escape. 
 

1 Thessalonians 4:13-5:3
 (from New International Version)