alt Hacker NewsIt's the length and depth of cold days in the winter that can potentially limit their breeding populations, is my understanding. So the issue is that more northerly areas are getting much more variance in temperature and lacking long deep consistent cold periods.
Up and down cycles in temperature have always been a thing on the North American continent but climate change has made it even more variable. We will still get places where it gets very very cold but not for the consistent chunks of time it takes to set back tick populations significantly.
TLDR I don't think it's the heat or cold per se but the variance.
And yes climate change is absolutely the prime factor in their spread. Into places where they were not ever a threat before.
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> So the issue is that more northerly areas are getting much more variance in temperature and lacking long deep consistent cold periods.
It impacts the population, but even a couple solid weeks of -20C weather doesn't seem to be enough to eradicate them.
I’ve seen a tick in Wisconsin every month of the year over the past five years or so. That is I’ve seen a January tick one year, February tick that same year or another year, etc. Whenever there is a bit of a warm spell they appear. Presumably small upward trends in temperature allows such warm spells to happen more frequently.