Is Manchester the UK's Wettest City?

No. Manchester averages ~808 mm annual rainfall—modest by UK standards. The wettest inhabited place is Llyn-y-cau (Llyn Cau) in Snowdonia, Wales, with ~4,948 mm. Among major cities, Glasgow (~1,124 mm) and Plymouth (~1,007 mm) are wetter. Manchester's reputation for rain stems from frequent drizzle and overcast days, not total volume.