California Climate Forecasts Signal Growing Risks for Tomato Crops

California’s tomato crops have taken it on the chin from extreme weather events in recent years, reducing supplies and hiking prices to the US food manufacturing industry. 

Gro’s long-term climate projections indicate that extreme weather risks will increase for California tomatoes in the coming decades. The state grows some 90% of all US processed tomatoes that go into cans and sauces.

Tomato production in California has declined in each of the past five years. Last year’s harvest slumped 50% year over year as the state endured “exceptional” levels of drought as measured by the Gro Drought Index, weighted for acres planted to tomatoes using Gro’s Climate Risk Navigator for Agriculture. 

This year, drought was replaced by early season heavy rains that flooded fields and forced farmers to postpone planting. The delays in planting could lead to reduced yields, as indicated by Gro’s Commodities Tracker, which is forecasting a “Medium” supply risk level — meaning supply is expected to fall short of historical levels — for the crop over the next six months. 

Still, increased planted acreage is projected to help boost 2023 California tomato production by double digits from last year’s weak output, which was the second-smallest harvest of this century. 

Tomato prices have reflected the California crop’s troubles. Shipping point prices, which are the cost of the product at the origin, for Roma tomatoes from central California exceeded historical highs for much of the current growing season, before settling back to average levels in recent weeks, as shown in this Gro display. 

Long-term climate forecasts signal that extreme weather will increasingly afflict California’s tomato-growing areas. By 2050, the state’s top tomato producing counties will see an average of 23.48 days per year when temperatures exceed 35C (95F), up from a projected 17.4 days in 2023, according to an analysis using the Gro Climate Ensemble model’s “medium-to-high” warming scenario, SSP3-7.0.

Processing tomatoes are especially vulnerable to extreme weather as they are mostly grown in open fields, unlike fresh tomatoes. Tomatoes grow best in daytime temperatures ranging between 21.1C and 29.4C (70F-85F). Temperatures significantly above or below this range can hamper tomato growth and quality. 

California’s main tomato-growing counties are also projected to see more intense rainfall. Gro’s Heavy Precipitation Indicator — which represents the 95th percentile of daily precipitation in a given area — forecasts a 4.4% increase in the magnitude of heavy precipitation events by 2050. 

The Gro Climate Ensemble, which was developed by Gro’s in-house team of climate and data scientists, uses raw climate data provided by a subset of labs that participated in the Intergovernmental Panel on Climate Change’s latest global climate change report to produce climate forecasts that reflect the collective knowledge of the world’s top climate research labs.