“Rah” doesn't have to be translated as “evil”, and in this instance it definitely shouldn’t be. That’s why different Bibles translate this verse differently. It is translated as "calamity" by the NASB and NKJV; "disaster" by the NIV; and "woe" by the RSV.
Contextually the verse is speaking of natural phenomena and human distress, not moral evil.
1 Thus says the LORD to his anointed, to Cyrus, whose right hand I have grasped, to subdue nations before him and to loose the belts of kings, to open doors before him that gates may not be closed:
2 "I will go before you and level the exalted places, I will break in pieces the doors of bronze and cut through the bars of iron,
3 I will give you the treasures of darkness and the hoards in secret places, that you may know that it is I, the LORD, the God of Israel, who call you by your name.
4 For the sake of my servant Jacob, and Israel my chosen, I call you by your name, I name you, though you do not know me.
5 I am the LORD, and there is no other, besides me there is no God; I equip you, though you do not know me,
6 that people may know, from the rising of the sun and from the west, that there is none besides me; I am the LORD, and there is no other.
7 I form light and create darkness, I make well-being and create calamity, I am the LORD, who does all these things.
8 "Shower, O heavens, from above, and let the clouds rain down righteousness; let the earth open, that salvation and righteousness may bear fruit; let the earth cause them both to sprout; I the LORD have created it. - Isaiah 45:1-8
Nothing about natural disaster.
