Dr. Chip Taylor of Monarch Watch shared his insights:

Monarchs continue to surprise. Estela Romero, who works extensively with Journey North, reported on Tuesday (3 April) that there were still 30 trees festooned with large clusters of monarchs at El Rosario. See Estela’s first hand account.

Cold temperatures stalled the migration's leading edge this week, concentrating the population in warm southern regions where eggs and larvae can grow quickly.