Here is a data source with recent recorded temperatures and monthly averages:
https://www.ncei.noaa.gov/access/coastal-water-temperature-guide/all_table.html#catl
Most are showing recent temps of just above 60 for area around Long Island, but averages say it should be dropping about a degree every 3 days.
How this matters - the basics are that you want to be in a position that when you fall in you are warm enough, long enough to have enough time to rescue yourself in whatever conditions made you fall over, and then warm enough while on your board to be able to get back to shore.
First challenge - when you fall in, the shock of being submerged in cold water causes some immediate issues (the colder it is and more exposed you are/less thermal protection you are wearing, the more likely & worse this could be). From https://www.weather.gov/safety/coldwater:
- Gasping for Breath & Rapid Breathing (2-3 Minutes or More) - Cold Water Immersion can trigger involuntary gasping, rapid breathing or hyperventilating due to the “shock” of sudden immersion. This uncontrolled rapid breathing can quickly create a drowning emergency if you inhale water and cannot stay afloat.
- Heart and Blood Pressure Problems - Cold water can cause a sudden spike in heart rate and blood pressure. This increase can cause heart failure and stroke for vulnerable people.
- Cognitive Impairment - Cold shock can cause an immediate panic, fear or stress reaction that then impairs clear thinking and decision making. Extended exposure and the onset of hypothermia can further hamper cognitive ability and the ability to choose the right actions to avoid severe injury or death.
Second challenge - the longer you are in the water and the colder the water, the faster heat is sucked out of you. In general, heat is sucked out of you when submerged some 25 times faster than if you were in air of the same temperature, so heat loss is fast. As your body loses heat, it protects itself by restricting blood to your arms and legs and keeping the warm blood at your vital organs. Major downside to this is that you become less and less coordinated as your arms and legs get less blood until you are incapacitated. Can happen as fast as 5-10 minutes in really cold water, so you need to be able to get back on your board reliably and quickly. There is also cognitive impairment, as talked about above.
Third challenge - getting back to shore after you remount your board. The prior 2 challenges primarily looked at water temperature. Once you are back on your board we finally would consider air temp. If the air temp is hot, then you likely are fine once you are back on your board even though you are wet. But if air temp is also cold, then being out of the water just slows the heat loss and the problems losing heat causes you. Having clothes on that will help keep you warm even when wet would help here. This is where cotton gets its nickname of “killer cotton”.
Putting all this together, I know my skills on a board (which are decent - I am mostly a kayaker, but do also SUP) and know how water down to about 50F impacts me and the 25 extra pounds of body insulation my body has gained. Based on this, I would be comfortable going out for a flat water paddle through November’s average water temps. I would probably wear at least some sort of wet suit or dry suit, but maybe not as much as called for by others (possibly a 3 mm farmer john). As water temp was headed to lower 50s, I’d switch to dry suit especially if air was also cool. I would definitely wear a life jacket and leash no matter what conditions (even in the heat of summer when the water temps feel like a bathtub).
But only you will know from experience whether and how bad cold water immersion shock is for you. And same for how fast you get cold and your body starts becoming less incapacitated. And only you would know how well you are at getting back on your board after falling in. All this takes experience, which is better gained at times when having experience to save yourself isn’t required.