3 years late!
I was considering getting down to two oils.
Then I realized that isn’t a big issue having some different oil on hand.
If I had a snowblower I would use 0W30, my mowers get 10W30, I keep SAE 30 and 15W40 for the generators in hot weather and use 10W30 or 5W30 if I need them in the winter.
Pressure washer is summer only - I tried 20W50 but think straight 30 or 15W40- maybe even some straight SAE 40 would be a better choice.
I take the view putting a correct oil in for the specific need is more important than a little bit of convenience of only having one oil to stock.
Considering your climate, you could switch to a 15w-40 HDEO for all of those.
All my summer OPE gets T5 15w-40, my winter OPE gets T6 5w-40. This includes a rider, walk-behind, power washer, snow blower and snow thrower.