I grew up in Northwestern Washington and I’ve done botanical fieldwork in Idaho the last four Summers so I have two responses to your question.
First off, I have spent a lot of time outside in Idaho and I can’t make any sense of where the ticks are and where they aren’t… In some places there are hundreds in the cat-tail marshes and in others there are none. Sometimes there are hundreds in the mid elevation forests and sometimes none. Until this year I had never ever seen one in the lowland sagebrush deserts but outside of Idaho Falls there are hundreds. I always thought it was way too arid for them in the deserts but nope, they can thrive there just like everywhere else. Just the other weekend I was at nearly 10,000 ft elevation in Western Montana and I sat down for lunch and not one but three ticks immediately started crawling towards me… It was so strange to see them at snow line and they failed miserably at stealth with no vegetation to hide beneath.
I spent ALL of my time outside on Whidbey Island growing up, crawling through the forest every day and I never encountered a single tick… Until two Summers ago I was visiting home and found not one, but two on my island… Such a horrible feeling. I’m used to dealing with tonnes in Idaho but it’s always so much worse when you are not expecting them.
I’m not sure what the population numbers are doing in Idaho but based on my experience and conversations with a few of my friends I think the populations are skyrocketing in Western Washington.
Also, please do be a little concerned about Lyme disease. My partner picked up Lyme in South Dakota and her life will never be the same as a result. If you get bit even once please get tested… It’s a myth that everyone gets a distinct rash and a lot of people show no symptoms until it is too late- the earlier you catch it the higher probability it can be treated successfully. If any doctor ever tries to tell you that Lyme disease can be cured with a simple course of antibiotics walk out of their office right then and there and find a Lyme literate doctor.