At the time of the death of a president (not necessary but usually done), to do an impeachment, when war is declared on the USA and there is a serious crisis in USA...like when Hurrican Karina hit the southern coast. I think there is another reason but I can't think of it right now.
Such would be a special session or perhaps a called session of Congress.
Emergency
A special session.
The President of the United States has the authority to call for a special session of Congress. This may be done to address urgent matters or to convene lawmakers outside of their regular schedule.
The president can call Congress into a special session. This occurs when the president believes urgent legislative action is needed outside of the regular session schedule. Special sessions can address specific issues or crises and are typically convened at the discretion of the president.
to address the economic crisis
He cannot forcibly prevent them from adjourning but he can ask to address them if he has some urgent message and call on them to act. He can call a special session if they are out of session.
Only the president can call congress into special session. Only 26 special sessions have been held,the last one was in 1948. The president can call congress or each of its houses. The senate has been called into special session 46 occasions last was 1933.
Yes, the President has the power to call Congress back into session after they have voted to adjourn in order to consider some pressing matter. He can also call just the Senate back to consider a treaty of appointment he makes. This power is granted under Article II, Section 3, clause 2. The constitution says that the president can convene congress under extraordinary circumstances for as long as he sees fit. Special sessions were called fairly often before the Senate and House began meeting for most of the year, but has only occurred four times since the 20th Amendment was ratified. The 20th Amendment calls for the first session of Congress to begin on January 3 each year. In recent years, the Senate and House have been authorized to call their own special sessions after Congress adjourns.
Because of the presidents power to call a special session
The special for Rep. Gabreille Giffords and all injuried or killed vitcims in the Tucson, Arizona shooting.
The Congress must meet on January 3 of each year to organize. After that they set their own meeting times. The President has the power to call special session of Congress if they are not in session already and something important comes up.