He won Iowa by almost 10 points in 2016 and 8 points in 2020. That state has only gotten more red since both those cycles. It would not be outlandish for him to pull 15% this go around based off those previous numbers and the current political makeup of the state. So 18% isn't that far off of expectations.
Now if you told me he was polling 18% somewhere like Pennsylvania, then yeah, that'd be kind of insane and much more noteworthy.
Yes... June is usually a mix of really nice summer days and cooler/wetter periods with troughing. This is true for most of the PNW and why the old adage in Seattle is that summer doesn't really start until July 5th.