Dandelion patches in Ottawa and across Eastern Canada have been playing host to hundreds of thousands of butterflies in recent days due to an unusually large spring migration.

Many of the butterflies are red admirals, which look like smaller versions of monarch butterflies.

Edward Bruggink is Carleton University's greenhouse manager. He says his students first noticed the unusual number of butterflies during research. (CBC)

Laura Drover was walking along the Rideau Canal Thursday, where hundreds of the butterflies were looking for dandelions.

"They're all over the dandelions, they're flittering all around, it's absolutely remarkable," Drover said. "(I don't usually see) this many at this time of the year in Ottawa.

"It's wonderful," she said. "It gives you something to chat about and to really enjoy the leisurely walk and see nature at its best all around you."

High temperatures in northern U.S. states combined with powerful winds are thought to have contributed to this spring's mass migration, said Edward Bruggink, Carleton University's greenhouse manager.

"It's a bit of a shock," Bruggink said. "Everything's out of whack. Things are not the way they should be at the moment.

"I hear next week it's going to be very cold, so it could be detrimental to the butterflies," Bruggink added.