Late spring is the sweet spot for Chicago. The bitter lake winds finally drop, the riverwalk opens up, and you can take an open-air boat tour past century-old skyscrapers without wearing three coats. You get Lou Malnati's or Pequod's with half the summer line, and the city actually feels relaxed.
A solid long weekend runs about $1400 once you factor in flights, a downtown room, boat tours, and plenty of pizza. Spreading that cost out over time keeps your monthly budget steady instead of wiping out your savings in one swipe.
The intro window is a deadline, not free money. If you still owe money after 15 months, the regular APR kicks in on whatever balance is left, which will quickly make that pizza trip a lot more expensive.