2015 was a major +PDO. I know people say that it doesn't matter, but in the last 20 years I've noticed a really good correlation, in some cases even exceeding ENSO.
Yes something to consider is I’d say a heatwave might have a slightly lower bar in say May or September than the height of summer.
I’d still say as advertised currently on the models a couple low 90s in mid June would not be a heatwave IMO. Just my opinion.