May to June and September to October work best—temps 15°C–25°C (60°F–75°F), festivals running, outdoor dining open, hotels not gouging yet. July-August hits 25°C–32°C (75°F–90°F), humid some days, but the lakefront stays breezy and the city's fully alive. November to March is brutal—temps -10°C to 5°C (15°F–40°F), wind off the lake cuts through everything, snow piles up, but hotel rates drop 40% and you see how locals actually live. It's advisable to book flights to Chicago in advance as last–minute flights can be expensive.
O'Hare Airport handles most traffic—direct flights from everywhere, international routes from Europe, Asia, and Latin America. Midway Airport, closer to downtown, often has cheaper fares on budget carriers. Domestic flights within the US run constantly. Book six to eight weeks ahead for decent rates. Flying Tuesday or Wednesday beats Friday-Sunday pricing. Some travelers choose Milwaukee airport, an hour north, when flight deals make the drive worthwhile.
US citizens don't need anything. Visa Waiver Program countries get 90 days with ESTA. Others need standard US tourist visas based on their passports.
Stop saving skyline photos—book your flight to Chicago and get to a city where the food is incredible, serious, and architecture matters. Winter separates tourists from people who actually want to be there.