From the U.S. State Department:
The Department of State warns U.S. citizens to carefully consider the risks of travel to Iran. Dual national Iranian-American citizens may encounter difficulty in departing Iran. U.S. citizens should stay current with media coverage of local events and carefully consider nonessential travel. ...
U.S. citizens should also review the Department of State's Country Specific Information for Iran and stay up to date by bookmarking the Bureau of Consular Affairs website, which contains the current Travel Warnings and Travel Alerts as well as the Worldwide Caution. You may follow us on Twitter and the Bureau of Consular Affairs page on Facebook as well; however, both Twitter and Facebook are filtered in Iran and will not be accessible without a virtual private network (VPN). If you don't have internet access, current information on safety and security can also be obtained by calling 1-888-407-4747 toll-free in the United States and Canada or, for callers from other countries, a regular toll line at 1-202-501-4444. These numbers are available from 8:00 a.m. to 8:00 p.m. Eastern Time, Monday through Friday (except U.S. federal holidays).
U.S. State Department Warning