Best Time to See Monarch Butterflies in Pennsylvania
August, September and July is the best time to see monarch butterflies in Pennsylvania. Based on 11,660 verified iNaturalist observations, here is exactly when monarch butterflies are most active across the year in Pennsylvania.
By Tim, founder of Easy Street Markets. I maintain the wildlife database and verify every animal and source myself. Updated July 2, 2026.
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 |
Weather to expect, source Open-Meteo
Typical weather in Pennsylvania
Recent typical conditions by month, so you can plan a trip around both when monarch butterflies are active and what the weather is doing. The best months to look for monarch butterflies sit around 57 to 86 degrees Fahrenheit, so pack for that.
| Month | Avg high | Avg low | Rain |
|---|---|---|---|
| Jan | 38°F | 23°F | 3.1" |
| Feb | 41°F | 23°F | 3.6" |
| Mar | 50°F | 31°F | 3.3" |
| Apr | 60°F | 40°F | 4.1" |
| May | 70°F | 49°F | 4.1" |
| Jun | 79°F | 59°F | 3.9" |
| Julbest time | 86°F | 65°F | 3.2" |
| Augbest time | 84°F | 64°F | 4.3" |
| Sepbest time | 75°F | 57°F | 3.9" |
| Oct | 64°F | 47°F | 4" |
| Nov | 51°F | 35°F | 2.4" |
| Dec | 43°F | 29°F | 4.3" |
Typical recent conditions (5-year means) from the Open-Meteo archive, averaged for Pennsylvania. Weather varies year to year, so treat these as a guide.
More on monarch butterflies in Pennsylvania:
Sightings of monarch butterflies in Pennsylvania peak in August, when 4,600 of the year's 11,660 verified observations are logged — about 39.5% of the annual total. Activity stays high through August, September and July.
The quietest stretch is January, when monarch butterflies are hardest to find — no verified records exist for January. If a reliable sighting matters, plan around the peak window rather than the off-season.
The monarch butterflies you are most likely to encounter in Pennsylvania are Monarch — the most-recorded species in the state. Each keeps its own seasonal rhythm, but the month-by-month pattern above reflects every reported sighting together.
Where to go
Best places to see monarch butterflies in Pennsylvania
- Appalachian National Scenic Trail — National Scenic Trail
- Captain John Smith Chesapeake National Historic Trail — National Historic Trail
- Chesapeake Bay
- Delaware Water Gap National Recreation Area — National Recreation Area
- Fort Necessity National Battlefield — National Battlefield
- Friendship Hill National Historic Site — National Historic Site
Frequently asked questions
What is the best month to see monarch butterflies in Pennsylvania?+
August is the single best month, and the broader peak window runs through August, September and July, based on 11,660 verified iNaturalist observations.
When are monarch butterflies hardest to see in Pennsylvania?+
January is the quietest month for monarch butterflies in Pennsylvania, with no verified records on iNaturalist.
Are monarch butterflies active year-round in Pennsylvania?+
Monarch butterflies are recorded in 11 of 12 months in Pennsylvania, so they can be seen year-round, with a clear peak in August.
More places to see monarch butterflies
More wildlife in Pennsylvania