When searching for a good deal, it’s best to be prepared for potential fluctuations in price. We recommend booking at least 44 days in advance, which can save you up to 20% on flights from Illinois to San Francisco compared to booking the week you need them. Waiting 44 days out may not be for everyone, so we have options available for flights within the next two weeks, with the lowest price starting at $117. For sooner than that we have options available in the next 3 days from $137.
February can be a great time to fly to San Francisco from Illinois with a flight ticket averaging about $121. Cheapflights users have found deals in the month of February for as cheap as $61. The most expensive prices can be found in the month of April.