Because of his illnesses, Ernest Hemingway was not able to get his novel to the publishers. Therefore, he had his wife, Mary Welsh Hemingway, summon his friend, LIFE Magazine Bureau Head Will Lang Jr., to leave Paris and come to Spain. Hemingway persuaded Will Lang Jr. to let him print the manuscript "The Dangerous Summer", along with a picture layout before it came out in hardcover. Although not a word of it was on paper, Ernest agreed to the proposal. The first part of the story appeared in LIFE Magazine on September 5, 1960. The other installments were printed in the following issues of LIFE.

In it, Hemingway describes the real-life bullfighting rivalry that took place the year before between legendary bullfighters Luis Miguel Dominguín the second and his brother in law Antonio Ordóñez. The two bullfighters wanted to prove who was better by each trying to kill more bulls than the other during 1959.

The title is perhaps foreshadowed in a phrase to be found in Hemingway's short polemical article "Who Murdered the Vets?: A First-Hand Report on the Florida Hurricane" (New Masses, 17 September 1935), where reference is made to the storm-damaged Florida Keys as "... these islands where there is no autumn but only a more dangerous summer ...".