Normandy

From the tour description on this site:

Day 8: Treasure of Bayeux This morning we'll take a walking tour of
Mont St-Michel's town and its towering abbey to learn about local
legends, monastic life, and the far-reaching influences exerted by
abbeys in French history. Then we'll drive into the heart of Normandy
to study the 1,000-year-old Bayeux Tapestry — a 70-yard-long
embroidered cartoon/work of art that brings to life William the
Conqueror's victory over the Anglo-Saxons at the Battle of Hastings in
1066. We'll enjoy dinner together and sleep in Normandy (2 nights). Bus: 2 hrs. Walking: strenuous.

Day 9: Normandy's D-Day Beaches We'll
spend the day with a local expert who will give us a powerful tour of
the Normandy beaches where, in June of 1944, the Allied D-Day landings
took place by sea and air. We'll visit Pointe du Hoc, where Army
Rangers scaled the cliffs in pre-dawn darkness, and the American
Cemetery, where 10,000 stark white markers memorialize the Americans
who gave their lives on the beaches below. We'll also visit the
strategic town of Ste-Mère Eglise, the airborne drop site made famous
by "The Longest Day" and "Band of Brothers." We'll return to our
Normandy home base in time for dinner on your own. Bus: 2 hrs.
Walking: strenuous.

So on Day 9 you will be going to the beaches.

Same clothes as the rest of the tour. Because the wind coming off the Channel can be quite biting I'd take a windbreaker or other layers.

Hi Kathy, I did this tour in mid-May 2009 and enjoyed it very much. The day we did the Normandy beaches it was raining, windy, and about 40 degrees. We had a picnic on the bus (fun, made the best of the situation). You will be with a local guide all day. Plan to be on the beaches for 1 or 2 hours, standing, walking a bit while the guide explains what happened there. As noted above, you'll also visit the cemetery and museum. I wore a rain jacket, jeans, and tennis shoes. Wish I would have had a fleece too, it was freezing.

I visited Normandy again in mid-May 2014. The weather was absolutely beautiful, 70 degrees, and sunny. I wore dockers, a short-sleeved T-shirt and took a fleece. So, it just depends.

Your packing list should include some type of rain gear in case you need it, and a fleece or sweater so you can layer.

We did the Paris and Heart of France in May 2013. The weather was mostly good, but I would dress in layers, and be prepared for occasional rain and wind. A wind and water proof shell would be good. You will actually walk down to both Utah and Omaha beaches, spending about 1 hour at each. So expect sandy and potentially wet conditions, shoes should selected for those possibilities. The Rick Steves tour description, as above, is pretty concise about the rest of the schedule in Normandy. You will have some extra time in the evening since you have free time after about 5 pm. Plus, in late May, the sun sets after 9:30 pm. Hope that helps.

Great advice above. It's hard to predict so definitely dress in layers. I brought a hat and a scarf and about three layers but it was sunny and calm in mid-May so I didn't really need all that but was glad I had it with me just in case. The weather can change even from hour to hour so you may be switching it up with every stop. You just never know so be prepared for anything.