I went last year in March, round trip from LA. The first few days and the last few days were windy and cold, which caused it to be a little rough, but other than that, it was beautiful weather and seas!
We've just done the cruise, 20th March to April 4th, out of the 8 sea days only 3 were good enough to feel comfortable around the pool, it was quite cold. Weather on the Islands was OK but not spectacular. We missed Kaua'i as the port authorities wouldn't let us in due to the heavy sea swell (weather was OK just roughish seas). Think twice if you are thinking of visiting Haleakala crater on Maui, the weather above about 5000ft was appalling, less than 100ft visibility, freezing cold and horizontal rain! Back at sea level it was great weather. We were told the crater weather was like this fairly regularly.
Having said all this please do not be put off, the ship is great and we enjoyed the holiday. If we had to change anything we probably would not have so long at sea.
We are also going on the 14 day LA to LA cruise in March. We will be on the Celebrity summit. What line and date are you going on? After checking out trips in January we decided we had a better chance of better weather in March realizing that in either month the weather out of LA could be iffy. I am looking forward to good weather in Hawaii. Hope our information is correct and good luck is with us!
Celeb Summit--March 12th (I think) RT LA-- Appreciate the tips about the crater & weather--guess we'll need a variety of clothes for sea days.Hoping it will be calmer next yr--this has not been a great yr!