I counted 6 days out of 23 for DAW, 4 out of 23 for SFM. Far from most. Bulk of which coincided with the heatwave. And isn’t that exactly what you’d expect in a +3SD airmass?
I think there’s an enhanced ageo flow due to mesoscale coastal front, max surface delta t/delta n, sets up regularly right along NH coast, where the Labrador current meets a cooked tropical airmass.