The big picture
There is no single “tick switch.”
Tick populations persist when the environment suits the tick and the animals it feeds on. Human risk rises when those systems overlap with where people live, work and spend time outdoors.
A longer window
Warmer conditions can improve survival, extend seasonal activity and make additional areas suitable for some tick species.
Hosts carry ticks
Birds and mammals can transport ticks into new locations. Local populations can establish where conditions support them.
Habitat meets daily life
Wooded edges, brush, leaf litter and fragmented green space can bring ticks, wildlife and people into closer contact.
The Public Health Agency of Canada says climate change is contributing to more ticks and tick-borne diseases in Canada, including longer survival, activity and season length, and more hosts expanding their range. Read the federal overview ↗
National surveillance
Reported Lyme disease cases have risen sharply.
Canada reported 143 human Lyme disease cases in 2010. The preliminary 2025 total is 7,105. That change is important—but it must be interpreted carefully.
*2025 is preliminary. Counts are reported cases, not the number of ticks. Source: Public Health Agency of Canada, accessed August 22, 2026.
| Year | Reported cases | Context |
|---|---|---|
| 2010 | 143 | Early national surveillance period |
| 2017 | 2,025 | Revised case definition introduced in 2016 |
| 2021 | 3,147 | National reported total |
| 2023 | 4,785 | National reported total |
| 2024 | 5,809 | Revised case definition introduced in 2024 |
| 2025 | 7,105 | Preliminary national total |
Surveillance totals reflect exposure, infection, health-care seeking, diagnosis, laboratory testing, reporting and the case definition in use. PHAC notes that revisions in 2016 and 2024 may affect comparisons across years.
What drives the change
Four forces are working together.
Suitable temperatures can extend activity above freezing, improve survival and lengthen the seasonal exposure window.
Migratory birds and mammals carry ticks. Deer help support adult tick feeding; small mammals can be important hosts for immature ticks.
Leaf litter, brush, wooded edges and some fragmented green spaces can support ticks and the animals they use as hosts.
Public awareness, clinical recognition, testing, surveillance and reporting influence how many human cases enter the official count.
This is why a regional question needs a regional answer. Canada is large, tick species differ, and risk can change across a province—even between neighbouring communities.
Common objection
“But winter was freezing.” Weather is not climate.
A cold day or snowy winter can affect tick activity, but it does not erase established populations. Ticks can shelter in leaf litter and beneath snow, while long-term temperature patterns affect where populations can persist.
One cold snap can pause activity. It does not reset the ecology.
Practical interpretation of long-term habitat suitability—not a forecast for every region.
The useful question is not “Did it get cold?” It is “Are conditions over time suitable for ticks, their hosts and human contact?” For personal decisions, current local public-health information is more useful than a national headline alone.
Practical meaning
More awareness should lead to a better routine—not less time outside.
You do not need to treat every outing as an emergency. Use layers that match your setting and keep a clear after-exposure plan.
Know the setting
Check local guidance and plan clothing and repellent for brush, tall grass, leaf litter and wooded edges.
Run a tick check
Check your body, children, gear and pets soon after potential exposure; shower and handle clothing as recommended.
Capture the facts
Remove an attached tick promptly, record timing and location, take photos and know when to seek medical advice.
ONPlan for your exposure
Going where ticks are part of the landscape?
An advance assessment can help eligible Ontario residents think through foreseeable or repeat exposure. A licensed clinician decides what is appropriate for each person.
Common questions
Canadian tick trends, answered.
Is climate change the only reason ticks are increasing in Canada?
No. Climate contributes to longer tick activity and survival in suitable areas, but animal hosts, habitat, land use, human exposure, surveillance and reporting also influence what Canadians see and what public health records.
Does one very cold winter eliminate ticks?
No. A short cold period does not remove established tick populations. Ticks can shelter in insulating leaf litter and snow, and long-term habitat suitability matters more than one day or one season.
Does 7,105 reported Lyme disease cases mean Canada had more ticks in 2025?
Not by itself. The preliminary 2025 case count measures reported human Lyme disease cases, not the number of ticks. Exposure, infection, diagnosis, reporting and case-definition changes all affect surveillance totals.
When is tick season in Canada?
There is no single safe off-season. Ticks may be active whenever temperatures are above freezing and the ground is not covered in snow, although activity varies by species, stage, place and time of year.
Are ticks only a problem in forests?
No. Wooded and brushy areas, tall grass and leaf litter are common habitat, but people and animals can carry ticks into yards, cottages and maintained green spaces.
Primary references
Sources and data notes.
- Public Health Agency of Canada: Ticks ↗
Canadian tick biology, activity, climate and geographic context. - Public Health Agency of Canada: Lyme disease surveillance ↗
Annual reported case totals and case-definition notes. - Public Health Ontario: Lyme disease ↗
Ontario surveillance and public-health resources.