INVERLOCH, Australia — They fled from looming firestorms that threatened to cut off their escape, only to join a slog alongside the masses of others who crowded the roads. Thousands more waited for rescue by sea.

Across the scorched southeast, frightened Australians — taking a few cherished things, abandoning their homes and vacation rentals, and braving smoke that discolored the skies — struggled Thursday to evacuate as wildfires turned the countryside into charcoal wasteland.

And from government officials came a disheartening warning: This weekend will be one of the worst periods yet in Australia’s catastrophic fire season.