The best time of year to visit Gettysburg is without a doubt in the spring or summer. If you want to get the best experience, you should visit between July 1-3. Every year, the town goes into ultra-patriotic celebration mode--not just because it is commemorating the battle, but because it is close to Independence Day. The only thing to keep in mind about visiting during this time of year is that it will be much more hectic than any other time of the year. Each year, Gettysburg sees about 2 million tourists, and this is their busiest time of year. However, it is for a good reason. Any time of year there will be re-enactments and plenty to see, but summer is the best time to visit because of the weather as well. Temperatures can get up to the 80's-90's at times, but overall the weather stays pretty consistent. If you visit in the months between September-June, you will have to deal with a lot of school children who are there on field trips with their classes. This isn't always such a problem, but if you do not like dealing with children you might want to avoid this, especially on the weekend. However, during the summer, this is a big location for families to go, so either way you are going to see some.