I thought we would have been slightly higher as well, 97-98F. Clouds weren't an issue here. Must have been a pocket of higher 850's over Long Island today.
Enhanced heating appears to occur immediately in advance of sea breeze fronts. E.g., see current temperatures 92-93F at coastal towns on the NJ shore.
https://www.njweather.org/maps/nj-statewide-air-temperatureshttps://www.njweather.org/maps/nj-statewide-air-temperatures
Yes, the sea breeze front is another factor that can contaminate that principle. If land breeze is not greater in force than the sea breeze, the areas within 5-7 miles of the coast will reach their peak 2pm or sooner.
The 10AM + 10 rule is a general principle that works [approximately], barring any significant airmass advection vicissitudes, or cloud cover, etc. So anyone at 90F by 10AM has a fairly good chance at 100F.
Rapidly spiked to 86F here with some breaks of sun in the past hour. If we continue occasional breaks, 850s definitely support 90. But we'll probably fall short.