The best time to visit Vernon truly depends on what sort of experience you're after, but generally, late spring to early autumn, from May to September, offers the most pleasant conditions.
If you're particularly keen on seeing Claude Monet's iconic gardens at Giverny in full bloom, then late spring (May and early June) is ideal. The gardens are at their most vibrant, with tulips, irises, and rhododendrons all showing off. The weather is typically mild and sunny, great for strolling through the flowerbeds and admiring the water lilies. This period is great for couples or solo travellers looking for picturesque scenery and a relaxed pace.
For those who prefer warmer weather and don't mind slightly larger crowds, July and August are excellent. The gardens remain beautiful, and the longer daylight hours mean more time for exploration. This is also a good time to enjoy the local markets and outdoor cafes. Families will find this period suitable, as the pleasant weather makes outdoor activities more enjoyable, and there are often local events happening.
Early autumn, specifically September, offers a lovely balance. The summer crowds begin to thin out, but the weather is still mild and agreeable. The gardens take on a different, but equally appealing, autumnal palette, and the surrounding countryside is beautiful.