When you see any source of fire, you may use your reaction to increase the heat and therefore the amount of damage that fire deals. The fire glows blue/white and the searing flame illuminates a 90 foot radius sphere with bright light and 30 feet of dim light beyond that. Any fire affected by this spell deals an additional amount of fire of radiant damage (your choice) equal to 1d6 + your spellcasting ability modifier. 

At Higher Levels. At higher levels, the extra damage increases by 1d6 for each level above 2nd.