Monarch Butterflies in Pennsylvania in September
Yes, September is one of the best months to see monarch butterflies in Pennsylvania. It is the 2nd busiest month of the year, with 2,821 of the 11,660 sightings logged across the year (24.2%), based on verified iNaturalist records.
By Tim, founder of Easy Street Markets. I maintain the wildlife database and verify every animal and source myself. Updated July 2, 2026.
Peak month for monarch butterflies in Pennsylvania
24.2%
of yearly sightings
2,821
records in September
#2
busiest month of 12
11,660
verified records a year
August 39.5%, September 24.2%, October 5.8%. Busiest month is August at 39.5%.
11,660 verified observations of monarch butterflies in Pennsylvania, recorded across 11 months of the year on iNaturalist.
When monarch butterflies are recorded in Pennsylvania
Peak month
August
4,600 records (39.5% of the year)
| Month | Observations | Share |
|---|---|---|
| January | 0 | 0% |
| February | 2 | 0% |
| March | 4 | 0% |
| April | 29 | 0.2% |
| May | 107 | 0.9% |
| June | 609 | 5.2% |
| Julypeak | 2,764 | 23.7% |
| Augustpeak | 4,600 | 39.5% |
| Septemberpeak | 2,821 | 24.2% |
| October | 677 | 5.8% |
| November | 42 | 0.4% |
| December | 5 | 0% |
Monarch Butterflies you are most likely to see
| Species | Verified observations |
|---|---|
| Monarch | 11,660 |
In Pennsylvania, September carries 24.2% of the year's monarch butterflies sightings, about 15.9 points above an even month-to-month split. That makes it the 2nd busiest of the twelve months, out of 11 months with recorded activity.
Activity is easing off from August (39.5%) into September, and it heads toward October (5.8%) after. This is right inside the peak window, so September is one of the surest months to plan a trip around.
The monarch butterflies most often recorded in Pennsylvania are Monarch. Those counts are annual totals rather than a September split, so treat them as which species you are likely to encounter, while the month figures above show how many sightings fall in September itself.
Which monarch butterflies you are most likely to see
- Monarch11,660 records
Plan your monarch butterfly trip in Pennsylvania
Start with live tours near Appalachian National Scenic Trail, then compare a nearby stay and a broader wildlife backup before you lock in the trip.
GetYourGuide
Live tours nearbySee live tours near Appalachian National Scenic Trail
Use the live GetYourGuide widget to compare local departures and activity styles close to the main monarch butterfly viewing area.
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Stay nearbyStay near Appalachian National Scenic Trail
Compare hotels, cabins and lodges close to the best monarch butterfly viewing area in Pennsylvania.
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Broader backupBook a monarch butterfly tour in Pennsylvania
Compare guided wildlife tours, boat trips and nature experiences if you want a second travel network beyond the live widget.
Frequently asked questions
Can you see monarch butterflies in Pennsylvania in September?+
Yes. September accounts for 2,821 of the 11,660 verified monarch butterflies sightings logged in Pennsylvania across the year, which is 24.2% of the annual total.
Is September a good time to see monarch butterflies in Pennsylvania?+
September is one of the best months. It ranks 2nd of the year and sits inside the peak window of August, September and July.
What month is best for monarch butterflies in Pennsylvania?+
August is the single busiest month, with the broader peak running through August, September and July, based on 11,660 verified observations.
Which monarch butterflies are you most likely to see in Pennsylvania?+
The most-recorded species in Pennsylvania are Monarch, based on all-time iNaturalist counts.
See monarch butterflies in Pennsylvania in other months
More wildlife in Pennsylvania