Residents in parts of southern and eastern Ontario, as well as Eastern Canada like Nova Scotia, are experiencing a surprisingly extended mosquito season this fall due to unusual weather patterns.
Warmer Temperatures Fuel Extended Activity
According to experts, a strong El Niño weather phenomenon combined with human-caused climate change has created warmer-and-humbler-than-usual conditions across the country. Laura Ferguson, an assistant professor in biology at Acadia University, noted that mosquitoes will remain active as long as they avoid consistent, freezing overnight temperatures capable of killing them. In Toronto and surrounding areas, where mosquitoes persisted into late October, temperatures reached the low 20s at the end of the month and early November. The Weather Network reported that Toronto has not recorded a freezing temperature since May 3.
Broader Implications for Health and Future Seasons
Bill Merryfield, a research scientist at Environment and Climate Change Canada, described the current El Nino event as exceptional, with warming exceeding three degrees. Researchers are examining how this prolonged season might affect Canada's 80 diverse mosquito species moving forward, potentially influencing winter survival rates and population sizes next spring.
Beyond the nuisance of bites and itching, experts warn that a prolonged season raises concerns regarding disease transmission. Marc Avramov, a PhD candidate at Carleton University studying mosquito-borne illnesses like West Nile virus and eastern equine encephalitis, noted that virus risks persist as long as cold fall conditions are delayed. Sustained mild weather could also allow new, winter-adaptive mosquito species to enter Canada and introduce emerging diseases.
