Alaska Airlines is offering discounts on flights to the Hawaiian Islands based on the size of the waves.

Surf-forecasting firm Surfline will supply the data, and Alaska says it will offer bigger discounts for days when the surf forecast is higher.

The promo, which Alaska is calling “Swell Deals,” will run from now until Nov. 8 and all travel must take place before Nov. 20. The discount is limited to Kauai (LIH), Kona (KOA), Maui (OGG), or Oahu (HNL) and are capped at 30% and will be determined by the following maximum swell heights:

At the time of publishing, the discount already reached 15% off. That means that you can currently escape to Hawaii as soon as tomorrow, Nov. 5, for as low as $260 round-trip from Los Angeles (LAX) to Kahului (OGG).

The data will come from 14 popular surf spots in Hawaii including Oahu South Shore, Hawaii Kona, Maui South, Kauai South, Kauai North, Maui West, Oahu North Shore, Oahu Windward Side, Maui North, Hawaii South, Hawaii Hilo, Oahu West Side, Lanai and Molokai.

The discount will be updated twice daily at approximately noon and 5 p.m. PST as Alaska gets the latest forecast from Surfline. You won’t have to worry about the discount dropping as it will remain the same unless the swells grow. For those who plan to take advantage of this deal, you can apply the discount on up to six passengers per reservation, but it will not count towards taxes and fees and cannot be combined with other discounts.

On top of the discount, Alaska is also waving oversize and overweight fees for sports equipment so passengers can fly with their surfboards for just $30. For MVP Gold 75K, MVP Gold, MVP, First Class and Alaska Airlines Visa® Signature Card holders, this equipment counts toward their free checked baggage allowance.

Related: The ultimate guide to flying with sports equipment 

“With the start of surf season in Hawaii, we saw an opportunity to further support our flyers’ passions by using the power of data to offer better deals as surf conditions improve,” Natalie Bowman, Alaska Airlines’ managing director of brand and marketing communications, said in the press release.

The airline wants to further use data to drive future deals, too. “By leveraging data, we can give people another reason to get on a flig­­ht, just when they want it most, to enjoy perfect conditions or take that bucket list trip that they might have otherwise missed,” Bowman said.

The airline has hinted that a similar deal may return when ski season begins — based this time on the expected amount of snow.

November is one of the best times to visit Hawaii for surfers, because that’s when the swells start building up. Even if if you’re not a surfer, you may find that this is a great time to visit Hawaii as it typically tends to be a bit more affordable. November is right before the peak season begins, so you may also enjoy a less-crowded vacation.

And of course, be sure to use a card that rewards you for your travels. Here are a few that we recommend: The Platinum Card® from American Express (5x on airfare booked directly with the airline), Citi Prestige® Card (5x on airfare), Citi Premier℠ Card (3x on airfare), Chase Sapphire Reserve (3x on travel), American Express® Gold Card (3x on airfare booked directly with the airline or amextravel.com) or Chase Sapphire Preferred Card (2x on travel)

This story was originally published on The Points Guy. Sign up for the TPG daily newsletter and wake up to unbeatable flight deals, travel industry news, and credit card bonuses that let you travel first-class to some of the world’s most incredible destinations at a fraction of the price.