Much different 500mb height tendencies today vs 2010, so we might see less chances to take advantage of the marine layer. But if the pattern legitimately permits, then we will get marine layers as "ferocious" as 2010. Book it! Not sure where your absolute certainty is coming from. For all we know, any subtle variation from 2010 as big we've already seen could mean more troughing for the second half of July in WA than fourteen years ago. The Canadian Prairie has been way cooler and wetter this June than in 2010, as an example, albeit an outlier one; the rule is warmer for most, I will admit! It's just that there are no certainties with the weather, ever.
Unless you're leaning into your 80-90% confidence right now to sound like a wizard in three weeks. Which is something I totally understand and would attempt myself.