The drive-in restaurant chain Sonic has cut in half the prices for its ice cream shakes on June 20 in a Summer Solstice promotion. Wednesday, June 20, is the longest day of the year in the northern hemisphere. The half-price deal will be available every night after 8 p.m. throughout the summer.

The Oklahoma City-based restaurateur also proclaimed itself "the official sponsor of the sun."

"When we looked at summer sponsorship opportunities for the SONIC brand, the sun quickly emerged as the ideal fit because of its unrivaled reach and exposure and Sonic long-standing association with the sun and summer. We believe summer tastes better at SONIC," said Chief Marketing Officer James O'Reilly.

Sonic has other dairy-related food specials, including a Chili Cheese Fritos Coney (a hot dog topped with warm chili, chili cheese Fritos corn chips, shredded cheddar cheese, onions and mustard) and a Wholly Guacamole Dog is a hot dog with pepper jack cheese, cheese sauce and other toppings. Both will be on the menu beginning in July.

Sonic has more than 3,500 drive-ins in 43 states coast to coast.