When is the ideal time for an eastern monarch to migrate south?

Using tagging data collected through Monarch Watch, a long-term community science program, Taylor et al. (2019) found that eastern monarch migration was most successful when monarchs followed a sun angle between 46.0° and 56.8° at noon. In southern Canada and the northern United States, the highest migration success was from early August to late September. In the central and southern United States, the highest success was from early September to late October. To learn more, check out this new map: How does timing affect monarch fall migration success?