Day of Fire/HeatPsa 21:9 Thou shalt make them as a fiery oven in the time of thine anger: the LORD shall swallow them up in his wrath, and the fire shall devour them. Although this doesn't specifically say "Day of the Lord" it does mention "time of thine anger" and "Lord...wrath" both phrases directly associated with describing the "Day of the Lord"
Zep 1:18 Neither their silver nor their gold shall be able to deliver them in the day of the LORD's wrath; but the whole land shall be devoured by the fire of his jealousy: for he shall make even a speedy riddance of all them that dwell in the land. Those (especially Christians) who are focusing their attention on things and wealth are going to have a rude awakening. The fire of God's judgment is going to level the playing field making everyone equal and subject to the same judgment.
Isa 34:9 And the streams thereof shall be turned into pitch, and the dust thereof into brimstone, and the land thereof shall become burning pitch. Kind of sounds like a Supervolcano
Joe 2:30 And I will show wonders in the heavens and in the earth, blood, and fire, and pillars of smoke. Nuclear mushroom clouds or supervolcano???
2Pe 3:7 But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men.
2Pe 3:10 But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
2Pe 3:12 Looking for and hasting unto the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat. "fervent heat", "pillars of smoke"...could all of this be describing a world-wide nuclear exchange at the end?
Joe 2:10 The earth shall quake before them; the heavens shall tremble: the sun and the moon shall be dark, and the stars shall withdraw their shining: