Does anyone know the actual tide value where the strand becomes passable? I've seen "between half-tides" and "an hour or two either side of low tide". Both are rather vague, given the variability of the actual low tide value. One of our group has an ancestor buried in the graveyard, but low tide is at a really bad time. Our only hope is to walk over as soon as it is passable to make it to Galway at a reasonable hour. Sheet 37 of the OSI Discovery Series might include the information.
Have a look at this website which gives a link to the tide tables. This should give a general idea of high and low tide so you can work out safe crossing times. It sounds as if the staff in Sweeney's shop/bar, Omey Strand Bar, Claddaghduff Ireland, are the experts and can give much more detailed information. They don't seem to have an email contact, but the phone number is 353 (0)95 44673. It may be worth contacting them nearer the time when you are in Ireland.
Thanks for the reply, but I had exhausted Google before asking the question. I have since found a marine chart that shows the tidelands to be at +6.0 to +6.5ft. The low tide on the day of our nearest travel is a +5.5ft, so there's only a one foot exposure. Assuming the tide follows a sinusoid, that gives me about 70 minutes on either side of low tide. That would be enough if it wasn't at 8:30pm and we didn't need to checkin to a Galway stay (82min+ drive). The following morning tide drops to +4ft, so that opens a four hour window centered on 8am - more doable if we want to leave Galway at 6am.
I did make contact with an Omey local, and although they didn't have the number I wanted, they stated that for a medium tide, there is +-3hrs centered on low tide. So our strategy will be to get there as early in that window as practical, and make our crossing as soon as it's walkable. They mentioned that even residents get caught out when the tides are distorted by surface winds.