Colias occidentalis
In 3 days ~10% in a week ~30%
Colias occidentalis, the western sulphur or golden sulphur, is a butterfly in the family Pieridae found in North America. Its range includes the Pacific Northwest and parts of British Columbia. The one flight period is from late May until early July. Its habitats include ocean bluffs, forest openings, mountain slopes, and subalpine meadows. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Olympic National Park | 🇺🇸 United States |
More parks will be added in future updates.
Rare
Under 5% of wildlife watchers report a Western Sulphur sighting in Olympic National Park on a given day, based on 38 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 113th most-seen of the 207 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
June and July
In those months about 10% of wildlife watchers report a Western Sulphur in Olympic National Park on a given day, against under 5% in August to May, the lowest months. Those are among Olympic National Park's driest months, with about 60 mm of rain a month against 370 mm in November.
Between 9 am and noon
Across all the parks we cover, that three-hour window holds the most Western Sulphur sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
Only Olympic National Park, in our data
Olympic National Park is the only park on Wallace's Line with enough records to rate Western Sulphur sightings: under 5% of wildlife watchers there report one on a given day.
Same family: Pieridae
The closest relatives of the Western Sulphur that you can see in Olympic National Park (family Pieridae, Whites, Yellows, and Sulphurs) are Margined White (about 20%), Pine White (about 10%) and Julia Orangetip (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Western Sulphur is recorded against all the insects logged in Olympic National Park (38 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
