Ashen winds

You gather up a thick cloud, and until the spell ends, ashes fall abundantly in a 100-foot-tall cylinder with a 75-foot radius centered on a point you choose within range. The area is lightly obscured, and you may change the direction of the wind in the cylinder, but not its strength.

When a creature enters the spell's area for the first time or starts its turn there, it is covered in a thin layer of ash and becomes vulnerable to fire damage. Upon leaving the area, or getting under cover, the ashes can easily be shaken off.

At higher levels: When you cast this spell using a spell slot of 2nd level or higher, the cylinder's radius is doubled for each slot level above 1st (75/150/300/600/1200/2400/4800/9600/19200 ft radius).