The best time to visit Aylmer and the surrounding area depends entirely on what you are there for. Birdwatchers should come in May for the spring warbler migration at Long Point (peak is often mid-May) or in October for hawk migration — Broad-winged and Sharp-shinned Hawks move through in spectacular numbers in September and October.
For beach visits at Port Burwell, July and August are the reliable months, with water temperatures that make swimming worthwhile. Summers in southwestern Ontario are warm and humid, with temperatures regularly above 30°C in July.
Spring and autumn are the most pleasant for driving through the countryside, when the tobacco and grain farms are either planting or harvesting and the roads are quiet.
Winter in Elgin County is cold and often grey, with lake-effect weather off Lake Erie. There is little reason to visit unless you are chasing winter birds.