Jims, I'd agree there is often a wind in the morning and evening as sea/shore temperatures are changing. And more wind to the east of Stony Brook.
But that still leaves a lot of hours in the day, typically from 9-10AM to 5-6PM, when there's nothing in the western sound and damned little west of Stony Brook or worse.
How many times has the ALIR fleet (usually the last weekend in July) rounded Montauk, come up around past Greenport, and then died, and sat without moving for the next 12 daylight hours?
I find July and August to be very much better chances of heat, humidity, and under two knots, than anything else I'd bet on. Not that there isn't some fine sailing to be had despite that--but if I had to plan ahead for 6-7 days to run all the way to Block and come back? Uh-uh, I'd want May, early June, or September.
You can get the last few years of mid-sound buoy data directly from:
NDBC - Historical Data Download
but I find 666 wind speed readings for all of last June, and their average comes out 4.02 knots. Not a lot of wind. Assuming I didn't get the math wrong.
July, 4.6 knots from 564 readings.
August, 4.9 knots, getting a little better--but not reflecting the temperature and humidity we've often had.
More meaningful if you run the numbers from more than one year, of course, they have them available.
The buoy data are interesting to work with, they plop nicely into Excel or Lotus. Fun to see if you'll be going dead downwind in 4 knots (ugh) as well as what the currents will be up to.
Me? I'd rather be in the Atlantic that time of year. Better wind, almost inevitably.