The short answer
54 degrees Celsius (130 degrees Fahrenheit) in water, or 6 minutes in a clothes dryer on high heat. Don’t count on cold weather to kill them.
Heat works
The most useful number for everyday life: a clothes dryer on high heat kills all ticks in as little as 4 minutes when clothing goes in dry. Researchers recommend 6 minutes to be safe. If the clothes are wet (say, you washed them first), it takes about 50 to 55 minutes on high heat because the dryer has to evaporate the water before temperatures get lethal.
In a washing machine, ticks die when water temperature reaches 54 degrees Celsius or above. Below that, they survive surprisingly well. All ticks in one study survived cold water washes. Nearly all survived warm washes. Even hot washes below 54 degrees only killed about half.
For more on the washer vs dryer question, see our post on whether ticks survive the laundry. The short version: dry first, then wash.
Cold does not
This is the part that matters for Ontario. Lab studies suggest ticks die somewhere between -18 and -10 degrees Celsius, but that temperature needs to be sustained for extended periods. A few cold nights won’t do it.
Research from Washington State University in 2023 found that while larval ticks were vulnerable to temperature extremes, nymph and adult ticks weathered both hot and cold conditions with little impact. They died mainly when they ran out of energy reserves, not from the temperature itself.
Southern Ontario’s winters are getting milder. In the Oakville area, we don’t get the kind of sustained deep freezes that would meaningfully reduce tick populations. Blacklegged ticks become active again as soon as temperatures stay above 4 degrees Celsius. Some species produce antifreeze compounds. Others overwinter under leaf litter, which insulates them.
This is why year-round tick prevention is increasingly recommended in our area. Tick season in Ontario starts earlier and ends later than most people expect.
Key takeaways
- A dryer on high heat for 6 minutes kills all ticks. This is the most reliable household method.
- Washing machines only kill ticks if water reaches 54 degrees Celsius or above.
- Ontario winters are not cold enough to reliably eliminate tick populations.
- Blacklegged ticks become active above 4 degrees Celsius, which in southern Ontario can be as early as March.
- Don’t rely on winter to solve your tick problem. Use year-round prevention and the dryer.
References
- Carroll, J.F. et al. (2016). “Killing blacklegged ticks in residential washers and dryers.” Ticks and Tick-borne Diseases. PubMed
- Washington State University (2023). “Ticks Prove Resilient to Extreme Temperatures.” news.wsu.edu
- Global Lyme Alliance. “Ticks Don’t Die When It’s Cold Outside.” globallymealliance.org
- EcoGuard Pest Management. “Do Ticks Die in Winter?” ecoguardpestmanagement.com