If you're moving to a college or university community, summer offers the biggest selection of apartments. However, because school is out, summer is the most popular moving season. This may mean you have fewer service options available.
In urban areas, the best time to move varies. People tend to stay put during the November and December holiday season, so you may see fewer apartment choices then. On the other hand, you may have a better chance at nice places that become available only toward the end of the year.
Late April is usually a good time to move. You can beat the busy summer season, and the weather is typically moderate.
Ultimately, the best time for your move depends on several things; some are beyond your control. Talk to your local Atlas agent. You'll get good advice and inside knowledge about the community you are moving into.