Before you pick a Halloween costume or sip this season's first pumpkin spice latte, purchase your Thanksgiving flight now to avoid soaring airfares later in the fall.

Booking your flight this week will save you, on average, 23% off the peak holiday booking price, according to data from travel booking app Hipmunk. The average ticket price the week of Oct. 1 is $387, while the average ticket jumps to $500 if you wait until the week before Thanksgiving when fares peak. That's a savings of more than $100.

And if you're traveling to a major city, booking early is critical since ticket prices, in general, are more expensive. For instance, if you're flying into San Francisco International Airport – the most popular Thanksgiving holiday destination according to Hipmunk – booking this week means you'll pay, on average, $461. After this week, flights jump up to $568.

Another tip to save money on your flight: If you can swing it, fly to your destination on Thanksgiving Day for significant savings. Avoid flying on Thanksgiving Eve, the most expensive day to fly.

See how much you can save in the 10 most popular Thanksgiving destinations by booking this week below.