Lasionycta caesia is a moth of the family Noctuidae. It occurs in the Cascade Mountains of northern Washington and the British Columbia Coast Range to 58 degrees north latitude.
It occurs in rocky alpine tundra near tree line and is nocturnal.
The wingspan is 30âÂÂ34 mm for males and 32âÂÂ35 mm for females. Adults are on wing from mid-July to mid-August.