According to the charity, about 80% of UK butterfly species have declined over the past 50 years due to factors including habitat loss, pollution and climate change.
Species that can be recorded during the survey include the Peacock, Holly Blue, Red Admiral, Brimstone and Small Copper.
Andy Hadley, BCP Council’s lead for climate response, environment and energy, said local habitats were important for a variety of butterflies and moths.
“Every 15-minute count helps build a clearer picture of how butterflies are doing locally and nationally,” he said.
Residents can submit their sightings using the free Big Butterfly Count app or through the organisation’s website.