France in April or May

Yes, probably more crowds but also more daylight, longer hours at attractions, possibly more-frequent buses in some places, and better weather. You can have a fine trip either time, but if all else were equal I'd probably go for late Spring.

Personally I would avoid Paris like the plague around May 1st as it is a HUGE holiday there. May 1 is on a Tuesday, so the city will be especially crammed probably from Friday through Wednesday.

I would choose May. Though in any given year it's possible that April weather could be better than in May, on average your chances for more agreeable weather are in May. Late May shouldn't be too bad for crowds, as it is not yet high season. Of course, Paris is incredible any time of year and in any kind of weather. I spent a couple of weeks there once in April and it rained most of the time and I still loved it. There's a reason the song "April in Paris" was written.

I went to Paris to meet up with my husband, who was there on business last year, mid-May. The weather was very pleasant, but not what you'd call warm. We did a lot of sightseeing in a short amout of time, and so we were out pretty early every day. We found that dressing in layers was the best way to go, since we were usually quite a distance from out hotel as the day got warmer. It only rained, for a short itme, one of the 5 days we were there. We hit all the highlights and didn't find anything overwhelmingly crowded. Took a lot of advice from Rick's book regarding lines at museums, etc. Have a great trip!

On average, there's not going to be much of difference in weather between those two time periods. Late April could be warm and dry and May could be cool and wet (as it was last year)... or it could be the opposite or something different all together. Nobody can predict this far out, so I would use other considerations beside weather guesstimates to choose your time.

The later time frame has a better chance of being slightly warmer and the days will be longer. I wouldn't worry about crowds, it is what it is. For your time frame I'd split the trip between Paris and Provence. The high speed train makes it very easy. A car rental with GPS in Provence is a good idea. This is based on my very limited experience.

We have been in France in April, mid May and the end of May. Eact year has been different. We found April to be lovely on two of our visits and May to be quite cool on another trip. I think it is really a guess at any season. The best suggestion is from Patricia and be able to dress in layers. Janis had good advice about May 1. May is the month of four public/bank holidays in France. May 1 will be on Tuesday this year. Everyone celebrates by giving little bouquets of lilies of the valley. You can buy flowers at florist shops and flower stands all over the small towns. Everyone travels. May 8 will be V-E Day and it is also on a Tuesday. Ascension Day is on Thursday, May 17, and since Pentacost is on Sunday, May 27, the following Monday, May 28 will also be a public holiday. Many French will find a way to make very long "weekends" during those weeks. People will be traveling all over the country and to Paris so reservations will be difficult to obtain. I would suggest having reservations made before you go. We had difficulty finding vacancies at the hotels where we wanted to stay. We also made the mistake of visiting Giverny on the Ascension Day holiday last year. I thought all of France had descended on the gardens. It took my husband over an hour to find a place to park even in the vicinity of the gardens. I was surprised to even find him again.
However, the flowers were beautiful! Early spring (April) will have the beautiful fields of yellow colza. The yellow fields, the blue sky and white Charolais cattle in the fields of green grass make rural France absolutely beautiful in spring. We didn't leave for France until the third week of May in 2011. The colza was gone. Iin April, you will have wisteria, pansies, tulips and daffodils. Near the end of May, there will be some roses. Have fun no matter when you go. I wish I was going this year!!!!!

We were there on May 1 and beyond. On that day we did a lot of walking, through the Jewish quarter to the Pompidou and elsewhere. In the afternoon we took a Paris Walks tour of Pere La Chaise cemetery and really enjoyed it. No trouble getting a restaurant table in the Marais. We really didn't notice that Paris was overcrowded.