CALGARY, Alberta, May 19 (Reuters) - Firefighters battling a wildfire that has threatened oil sands facilities north of Fort McMurray, Alberta looked to cooler weather and the promise of rain on Thursday, as the city's evacuated residents were buoyed by long-awaited re-entry plans.
The fire, spread over 422,000 hectares (1.04 million acres), surged north of Fort McMurray this week, forcing the evacuation of 8,000 oil sand workers and prolonging a shutdown that has cut Canadian oil output by a million barrels a day.
"We expect lighter winds and continued humidity to rise as we start to see some potential for rain, or at least cooler weather, over the next couple of days, which will be a real bonus," wildfire manager Chad Morrison said on Wednesday.
Evacuees who fled Fort McMurray two weeks ago as the massive blaze breached the city may be allowed to return home as soon as June 1, officials have said, if air quality improves and other safety conditions are met.
Oil sands operations directly north of the city stayed shuttered, as firefighters hold back a blaze that threatened the mining and upgrading projects of Suncor Energy and Syncrude Canada.
The fire destroyed a 665-room lodge for oil sands workers on Tuesday, before blazing eastward toward other camps, but officials said they were not aware of further industry damage.
"In terms of the industrial camps and facilities out there, we have been able to hold the line," Morrison added.
The lengthy shutdown in energy output has dealt a new setback to producers, suggesting production may be suspended for longer than companies and analysts had originally anticipated.
But there were glimmers of hope. Premier Rachel Notley said on Wednesday that some of the region's 90,000 evacuees would be able to return home early next month, if it was safe to do so.
That excited residents, though they were nervous about what they might find.
"It's exciting news, but you are also scared to see what you get when you get back," said Fort McMurray resident Ria Dickason, adding that she was concerned about smoky air.
The air quality health index, which usually stands between 1 and 10, hit 51 on Wednesday morning, before improving to 11.
"We won't go back if it's anything close to the levels it's at now. My daughter has asthma, so we are more alert to it," Dickason added.
Writing by Julie Gordon in Vancouver; Editing by Clarence Fernandez