With NTP last year, by the time we got to the serious OWS part, the water temperature wasn't an issue. Having been in the pool all winter long, I'm itchin' to get back in the open water. OTOH, I'm kinda a wuss and not a big fan of being uncomfortable.
I really don't have any frame of reference for water temperature. I wasn't able to join everyone who went to Lake Anna last weekend, but was surprised that no one mentioned (complained about) water temperature, which was about 60 degrees according to the power plant website.
Granted everyone is different, but any general guidelines for when "that was no fun" turns into "that was cold but OK' turns into "that was chilly but decent" turns into "that was not half bad"'?
About Lake Anna, it's the cooling lake for a nuclear reactor. So the water is always a bit warmer than what is 'natural.'
60 is still a bit chilly once you put your face down but you get over it pretty fast. I think 55 is real chilly once your face goes in but 50 is probably manageable if you're brave. A few years ago I did Columbia Tri when the water was in the low 50s. I stupidly stood around knee deep in the water until the gun sounded and when I started swimming I nearly freaked out. The lesson learned is to get in the water and swim for a couple of minutes. By the time you get started, you'll have adjusted to the cold.
You can always buy neoprene booties and cap if you are really sensitive to the cold. Or double up on swim caps for a little extra protection from the cold.
If you do head out to swim in water that is sub-60, I would highly suggest that you go with a group. It's even more important when conditions are less than optimal because you just never know.
I think there is a DC Tri group heading out at 11 on Saturday to swim at Sandy Point if you are really motivated to try some OWS.
Last weekend at Lake A I believe we were quoting 63 degree water. That was cold enough that people freaked when they first got in, but once they got going it was ok. Some folks wore neoprene caps and said they were happy they tried that. Thank you nuclear power (the best current option to get us off of fossil fuels).
Maybe 32 degrees:
I went out to Sandy Point earlier today. Water temp is around 54-55. It was cold enough that it took 4 or 5 attempts before I could keep my face in the water for more than a few breaths. But after that it wasn't too bad.