Summer vacation is right around the corner, which means it’s time to book flights. And if you want to find the best possible price, you might want to book this week.

According to flight, hotel, and car rental search engine Hipmunk, the best time to book flights for summer travel is the week of April 23.

“U.S. travelers should book their summer travel the week of April 23 to maximize domestic flight savings — do so and you can save up to 12 percent compared to those who wait until mid-June, when booking prices for summer peak,” the site's study states.

If you're planning to travel for Memorial Day, Hipmunk recommends booking your flight the week of Monday, April 23 to save up to 16 percent. And if you book your Fourth of July flights the week of April 23, they say you could also save 14 percent.

If you wait too long, flight prices will likely skyrocket. (Booking too late — or too early — is the most costly mistake you can make, according to airfare forecasting app Hopper.) According to Hipmunk’s analysis, Sunday, June 10 is the most expensive day to book any summer travel.

Airfare aggregator Skyscanner found that the top trending domestic summer destinations are New York City, Las Vegas, Miami, Los Angeles, and Chicago. The average Las Vegas flight, however, has dropped in price 14 percent compared to last year. Other top destinations with year-over-year price drops include Reykjavik (down 27 percent), Denver (down 19 percent), Tampa (down 16 percent), and Hong Kong (down 11 percent).

But if you can't be flexible when choosing your destination, try to be flexible about the days you travel. As Hipmunk noted, 8 percent of all summer bookings are for the Fourth of July. Additionally, three of the four busiest summer departure days revolve around the Fourth of July, including the Friday before, June 29, 2018. It’s also the most expensive departure date for those traveling for the holiday.

But, if you really have to wait a week to book your Fourth of July travels, you should be OK. According to Hipmunk, the average flight booked the week of April 23 will cost $278. If you wait to book during the week of April 31 it will only set you back an additional dollar, at $279.