Hi, I was in Newfoundland the first week of September last year and the weather great....sunny and warm if not hot on a couple of days.
I took the ferry over from North Sydney to Port aux Basques and returned on the overnight 14 hour crossing from Argentia after driving across to St. John’s. A straight coast to coast run on the Trans Canada in 950 kms but get off the TCH and explore the side roads into smaller communities.
And definitely take the short ferry ride to Fogo Island.....incredible! Temp was in the mid 20s and sunny the day I was there but the icebergs were still quite visible off the coast.
You’ll also want to visit Gros Morne National Park......a UNESCO World Heritage Site.