A heatwave in Southern California's major lemon growing region this month caused a loss of lemons and a squeeze in supplies, which has driven up wholesale prices about 40 percent or more in some markets.

"This demand exceeds supply situation will last until September/October at least." said Joel Nelsen, president of the California Citrus Mutual, a citrus producers trade group.

Terminal prices of fresh lemons in Los Angeles have risen about 40 percent or more since June 1, according to U.S. Department of Agriculture data. The price for cartons of lemons (sizes 95-115) at wholesale was $36 to $39 on June 1 and as of last Friday was $52 to $55.

"They're shooting up pretty high right now," a Los Angeles-area produce market specialist who didn't want to be identified told CNBC on Monday. "I heard it's like 70 bucks on the street now."

Ventura County, the leading region in the state for lemon production, suffered from record-breaking temperatures in early July at the tail end of is harvest season. Temperatures in portions of the county reached a high as 114 degrees on July 6 and hit the century mark again the next day in some growing areas.