2 Peter 3:10

10 But the day of the Lord will come like a thief, in which the heavens will pass away with a roar and the elements will be destroyed with intense heat, and the earth and its works will be burned up.

“The day of the Lord” refers to the judgments of the Lord during the time of the Tribulation, and then also, 1000 years later at the end of the millennial kingdom before the creation of the new heaven and new earth.

The coming of that day, “like a thief,” indicates that His judgment will be sudden, unexpected, and disastrous, especially to the unprepared. 

The next phrase, “the heavens will pass away with a roar and the elements will be destroyed with intense heat, and the earth and its works will be burned up,” is descriptive of what will happen during both the Tribulation and the destruction of the earth and the universe after the millennial kingdom. However, as I mentioned earlier, the destruction and the burning during the Tribulation is just on the surface of the earth, but the entire destruction of the earth and universe will come at the very end. This verse seems to refer mainly to that final destruction (referred to again in verse 12).