Bad weather forced the cancellation of President Bush's trip Wednesday to the Boy Scouts' national jamboree where tens of thousands of youngsters have been saddened by the deaths of four of their leaders in a tragic accident.

The president was to have flown by helicopter to the National Boy Scout Jamboree being held at Fort A.P. Hill, an Army base about an hour south of Washington. But Bush's appearance, as well as the entire schedule of evening events at the jamboree, were scrapped at the last moment because of the threat of severe thunderstorms and strong winds. About 300 Scouts also were treated for heat exhaustion and dehydration as temperatures hit close to 100 degrees.

The White House said Bush would instead travel to the gathering on Sunday evening, at the request of the organizers.

At the last jamboree four years ago, Bush's trip was also canceled because of bad weather, in which lightning strikes caused minor injuries to two Scouts. He spoke to the group a day later by videotape.

White House press secretary Scott McClellan said the Scouts had recommended that Bush not come and that the evening events be canceled on Wednesday. Renee Fairrer, a spokeswoman for the Scouts, said it was a joint decision and was driven mostly by a concern for the safety of the children and tens of thousands of visitors.

Earlier, McClellan had said that Bush's visit would be "a moment to keep in our thoughts and prayers the families of those four parents who tragically lost their life earlier this week."

The four Scout leaders died Monday while erecting a large dining tent at the gathering. Military and Scout officials were investigating the incident, in which the adult Scout leaders lost control of a huge center pole, sending it into nearby power lines. The men burned to death in front of stunned children.

The 10-day event, which draws 40,000 Scouting enthusiasts from around the world for camping, fishing, archery and merit badge competitions, was closed to visitors Tuesday as Scouts reviewed safety procedures and mourned the four men but was trying to get back on schedule Wednesday when weather interfered.