Snakes in Illinois in September
Yes, September is a good month to see snakes in Illinois. It is the 5th busiest month of the year, with 2,645 of the 26,776 sightings logged across the year (9.9%), 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 June 28, 2026.
Good month for snakes in Illinois
9.9%
of yearly sightings
2,645
records in September
#5
busiest month of 12
26,776
verified records a year
August 6.2%, September 9.9%, October 15.2%. Busiest month is April at 21.4%.
26,776 verified observations of snakes in Illinois, recorded across 12 months of the year on iNaturalist.
When snakes are recorded in Illinois
Peak month
April
5,721 records (21.4% of the year)
| Month | Observations | Share |
|---|---|---|
| January | 33 | 0.1% |
| February | 123 | 0.5% |
| March | 1,917 | 7.2% |
| Aprilpeak | 5,721 | 21.4% |
| Maypeak | 5,333 | 19.9% |
| June | 3,204 | 12% |
| July | 1,667 | 6.2% |
| August | 1,665 | 6.2% |
| September | 2,645 | 9.9% |
| Octoberpeak | 4,068 | 15.2% |
| November | 346 | 1.3% |
| December | 54 | 0.2% |
Snakes you are most likely to see
| Species | Verified observations |
|---|---|
| Common Garter Snake | 4,171 |
| Common Watersnake | 2,963 |
| DeKay's Brownsnake | 2,819 |
| Northern Cottonmouth | 2,703 |
| Plains Garter Snake | 2,246 |
| Gray Ratsnake | 1,446 |
| Eastern Foxsnake | 1,002 |
| North American Racer | 846 |
In Illinois, September carries 9.9% of the year's snakes sightings, about 1.6 points above an even month-to-month split. That makes it the 5th busiest of the twelve months, out of 12 months with recorded activity.
Activity is rising from August (6.2%) into September, and it heads toward October (15.2%) after. The busiest month is April (21.4%), so if timing is flexible, that window is the safer bet.
The snakes most often recorded in Illinois are Common Garter Snake, Common Watersnake and DeKay's Brownsnake. 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 snakes you are most likely to see
- Common Garter Snake4,171 records
- Common Watersnake2,963 records
- DeKay's Brownsnake2,819 records
- Northern Cottonmouth2,703 records
- Plains Garter Snake2,246 records
- Gray Ratsnake1,446 records
Plan your snake trip in Illinois
Start with live tours near Lewis & Clark National Historic Trail, then compare a nearby stay and a broader wildlife backup before you lock in the trip.
GetYourGuide
Live tours nearbySee live tours near Lewis & Clark National Historic Trail
Use the live GetYourGuide widget to compare local departures and activity styles close to the main snake viewing area.
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Stay nearbyStay near Lewis & Clark National Historic Trail
Compare hotels, cabins and lodges close to the best snake viewing area in Illinois.
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Broader backupBook a snake tour in Illinois
Compare guided wildlife tours, boat trips and nature experiences if you want a second travel network beyond the live widget.
Gear to see them
Frequently asked questions
Can you see snakes in Illinois in September?+
Yes. September accounts for 2,645 of the 26,776 verified snakes sightings logged in Illinois across the year, which is 9.9% of the annual total.
Is September a good time to see snakes in Illinois?+
September is the 5th busiest month. It is workable, though April and May is the stronger window for a reliable sighting.
What month is best for snakes in Illinois?+
April is the single busiest month, with the broader peak running through April, May and October, based on 26,776 verified observations.
Which snakes are you most likely to see in Illinois?+
The most-recorded species in Illinois are Common Garter Snake, Common Watersnake and DeKay's Brownsnake, based on all-time iNaturalist counts.
See snakes in Illinois in other months
More places to see snakes