Flight Threshold
A monarch is paralyzed by cold temperatures. It can't fly unless its flight muscles are at least 55°F. On a cool day, a monarch can bask in the sun to reach flight threshold.

"At 10:30 the butterflies that were warmed by the morning sun were flying around and those in the shade were still hanging in the trees."
                                                                                   —Tanner Hanson

Christy Smith