A jury awarded more than $289 million to a former school groundskeeper who claimed he was diagnosed with terminal cancer after using Monsanto Co.’s weed killer.

The jury, in San Francisco Superior Court, found that Monsanto had failed to warn about the dangers of Roundup and Ranger Pro, both herbicides, and awarded $39.2 million in compensatory damages and $250 million in punitive damages to Dewayne “Lee” Johnson.