For the third consecutive ranking, Chicago is the worst city in America for rats, according to a new study from the pest control company Orkin.

It ranked cities by the number of rodent treatments the company performed over the past year.

Rodent season is upon us…

Fall is the start of rodent season, so unwanted pests like rats and mice will begin to seek out food, water and shelter to survive the winter.

How big of a problem is this? An estimated 20 million rodents invade homes in the U.S. every year.

“Rats and mice begin looking for warmer, more insulated places to get through the winter, and these too often happen to be our homes or businesses,” said John Kane, entomologist and Technical Director of Orkin’s Midwest Region. “Rodents like to chew on wood and electrical wires, increasing the fire danger behind your walls and potentially damage to your home.”

Getting inside isn’t a problem for them. Rats can squeeze through a hole the size of a quarter, and mice can fit through a hole the size of a dime.

And even if they can’t find an opening, they can often chew their way inside your home!

RELATED: 5 natural ways to get rid of pests

Orkin: These are the top 50 rattiest cities in America

1. Chicago
2. New York
3. Los Angeles
4. San Francisco ‘ Oakland
5. Washington, DC
6. Philadelphia
7. Detroit
8. Baltimore
9. Seattle ‘ Tacoma
10. Dallas ‘ Ft. Worth
11. Denver
12. Minneapolis ‘ St. Paul
13. Cleveland ‘ Akron
14. Atlanta
15. Boston
16. Hartford ‘ New Haven
17. Portland, OR
18. Miami ‘ Ft. Lauderdale
19. Indianapolis
20. Houston
21. Milwaukee
22. Pittsburgh
23. New Orleans
24. Cincinnati
25. Richmond ‘ Petersburg
26. Sacramento ‘ Stockton
27. Kansas City
28. Charlotte
29. Norfolk ‘ Portsmouth ‘ Newport News
30. Buffalo
31. Columbus, OH
32. St. Louis
33. Raleigh ‘ Durham
34. Grand Rapids ‘ Kalamazoo
35. San Diego
36. Albany ‘ Schenectady
37. San Antonio
38. Tampa ‘ St. Petersburg
39. Rochester, NY
40. Nashville
41. Champaign ‘ Springfield ‘ Decatur
42. Greenville ‘ Spartanburg
43. Memphis
44. Phoenix
45. Syracuse
46. West Palm Beach
47. Orlando ‘ Daytona Beach
48. Madison
49. Flint ‘ Saginaw
50. Green Bay ‘ Appleton

Worried about rats and mice? There are some things you can do to keep rodents out of your home without having to hire an expensive pest control company.

Here are six tips from Orkin to prevent rats and mice:

• Inspect both inside and outside the home for rodent droppings, burrows and rub marks along baseboards and walls.
• Look for possible entry points outside the home and seal cracks and holes if any are found. Rodents prefer spaces that are hidden, dark, warm and difficult to reach.
• Install weather strips around entryways, especially under doors, to help block rodents from sneaking inside.
• Store food properly by keeping it sealed tightly in rodent-proof containers like plastic bins or metal canisters.
• Clean up crumbs and spills as soon as they happen to avoid leaving food residue or sugary substances that can attract rodents.
• Cut back trees and bushes to at least three feet away from homes to avoid giving rodents a “jumping off” point to access the gutters, roof or other hidden openings.

To control other pests like spiders and roaches, a few of us at Clark.com have fired the big pest control companies and started doing the work ourselves for a fraction of the price.

Read more about how easy (and cheap) DIY pest control can be!

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