Summer/Winter tires in the shoulder seasons

You don't have a third set of wheels for all seasons for the month on either side? For shame!

In all seriousness, I wait until average nightly lows are below freezing and daily highs are below 50 for a solid week to change over. Reverse in spring, although I usually delay a couple/few extra weeks to allow for road repairs and the random late season snow storm.

I change over usually around mid November, when the mountains start to open. Seattle is usually in the 30s-50s all winter and the tires do fine. Morning and rainy commutes are more of a risk on summer compound in our usual conditions than the risk from winter tires at 50 degrees.

winter tyres wont grip as hard in super warm temps but they wont degrade in them either. Once the daily high is consistently in the low to mid 40's is when I would swap.

^^^
What he said. Most winter tires suggest a swap over when highs are 45 degrees in general most parts of the country U.S. that’s right around November, middle of November.