Summer came too early to Europe’s most important rice-growing region, and weeds are taking over Sharon Angoli’s parched paddies in Italy’s Pavia province. “That one is done for, no matter what happens,” the 22-year-old said as she surveyed one desolate field that has been baked by what is among the most severe heatwaves to hit the continent in June. Even abundant rains for the rest of the summer would probably not save the crop, she said. Angoli and her father, Carlo, also fear for their other...