Based on 753 research-grade iNaturalist observations in Montana, California Tortoiseshell is most often recorded in July; in Montana it behaves like a summer visitor / breeder. It ranks #1 among butterflies recorded in the state in our data.
Nymphalis californica
California Tortoiseshell in Montana by month
Bars show research-grade observations per month. They mix true seasonality with how often people are outdoors, so treat small numbers with caution.
Also seen in Montana in July
Essex Skipper
Field Crescent
Common Wood-Nymph
Lorquin's Admiral
Small Wood-Nymph
Boisduval's Blue
Western Tiger Swallowtail
Milbert's Tortoiseshell
Places to look in Montana
National ForestBitterroot National Forest
State ParkMakoshika State Park
National ForestBeaverhead–Deerlodge National Forest
National ForestLewis and Clark National Forest
National ForestHelena National Forest
State ParkMadison Buffalo Jump State Park
FAQ
When does California Tortoiseshell appear in Montana?
Mainly July–September, with the most records in July.
How common is California Tortoiseshell in Montana?
It ranks #1 by number of iNaturalist observations among butterflies in Montana (753 records in our sample).