The actor - who plays Jon Snow on HBO's fantasy drama - told Collider that the new episodes have been allocated a bigger budget.
"I'd definitely say our budget's bigger for season three - you can feel it on set," Harington told Collider.
"I'll put it this way: season one was a big impact season, season two was more story[-led], season three is another impact season."
The 25-year-old added that the show's third season is his "favourite season so far".
"There's some wonderful stuff coming in this season which is gonna grab people, especially if they don't know what's coming," he promised.
Despite the show's success, Harington also claimed that a fourth season of Game of Thrones is not yet a certainty.
"We don't know whether we're coming back for a fourth season - we won't know until just before we [start filming] and I just take it season-by-season," he explained. 'Maybe we are [coming back] but I think it's foolish to assume."
Game of Thrones returns to HBO on March 31, 2013 and airs on Sky Atlantic in the UK.
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