Detroit's best months are May through October. Late spring and summer mean the riverfront patios, festivals at Hart Plaza (Movement in May, Jazz Festival over Labor Day weekend), Tigers baseball at Comerica Park, and warm evenings on the RiverWalk. The Detroit International Auto Show, NAIAS, used to anchor the January calendar and now runs in September.
Winter is genuinely cold — long stretches below freezing from December through February, with significant lake-effect snow possible. Indoor attractions (the DIA, Henry Ford Museum, Motown Museum, Masonic Temple) are open year-round and uncrowded in deep winter. Spring is wet and unpredictable; autumn is reliably beautiful, with foliage colour into late October.
Big weekend draws are the Jazz Festival (Labor Day weekend), Movement (Memorial Day weekend), the Thanksgiving Day Parade on Woodward, and the Ford Fireworks over the river in late June.