Record drought and heat have some farmers worried about where and when crops can be grown in the future, even in California where unprecedented microclimate diversity creates ideal growing conditions for many of the most popular items in America's grocery stores. A third of the vegetables and two-thirds of fruits and nuts consumed by Americans are now grown on more than 76,000 farms across the state, yet 20 years from now certain California regions may simply become too hot and dry for continued production.