Dover has a mid-Atlantic climate — hot and humid in summer, mild in spring and autumn, cold but rarely severe in winter. The most comfortable visiting months are April through June and September through October, when temperatures are pleasant and the historic downtown is at its best.
The two NASCAR race weekends — typically in May and October — bring enormous crowds to Dover. If you plan to attend a race, book accommodation well in advance and expect traffic on Route 13. If you are not attending a race, these weekends are best avoided entirely. Delaware State Fair in late July is a significant local event that draws crowds from across the state.