The Chill Factor

Inspiration

California's orchards need cold winters. A Kerman pistachio tree needs about 800 chill hours to bloom well. After the warm 2015 winter, California's pistachio crop fell 47%, from 518M to 275M lb. Central Valley chill has dropped by up to 30% since 1950. Warm winters also hit what people eat: after the 2024-25 winter, some peach growers lost 30% of their crop or all of it, and peach prices rose 17-23¢/lb (CBS News, Aug 2025). USDA ERS research shows low-income households buy less fruit when prices rise. UC Davis FNRIC challenged us to give growers better chill data, and we took it on.

What it does

The Chill Factor gives growers orchard-level chill hours, so they see what their own trees experienced instead of relying on a CIMIS station up to 50 km away. Growers get one number and one color (green, yellow, red) comparing this season to past years, plus a forecast. Investors, lenders and land buyers get a long-term view of how reliable chill has been at a site. Growers can use it to time rest-breaking sprays, forecast bloom, check whether sprinkler cooling is adding chill, and choose what to plant.

How we built it

We built a multi-source data engine that blends CIMIS hourly station data, FNRIC sensors, PRISM and Daymet gridded data, the NWS National Blend of Models, and 16-day forecasts. It rebuilds hourly temperatures from daily highs and lows, so a low-cost orchard sensor only needs to send one message a day.

Challenges we ran into

Weather stations are sparse, sometimes get removed, and miss microclimates like foothills and elevation changes. Orchards often have poor connectivity, so data arrives with gaps. Blending sources that differ in resolution and reliability, and showing it all simply enough for a busy grower to read at a glance, was the core challenge.

Accomplishments that we're proud of

We turned a complex, multi-source climate calculation into a one-glance verdict for growers. We also built an economic case: for a 1,000-acre pistachio operation, we estimate that a bad-chill year puts about $3.75M at risk and that acting early could protect $375K-$940K, for a $5,000 subscription. In a good year, growers could save an estimated $80K-$200K by skipping sprays they don't need.

What we learned

Chill is a whole-crop risk for orchards that must stay productive for decades, yet growers often dig through past years by hand to judge it. Growers want a simple answer: is this year good or bad? Climate risk to farms is also a health risk, because it affects the price and availability of fruit and nuts.

What's next for The Chill Factor

We plan to deploy and maintain our own in-orchard sensors to build a proprietary field dataset. Every orchard we add improves the estimates for its neighbors. We will also train an AI yield model, add more chill models (Utah, Dynamic) and growing degree days, and map the regions losing chill fastest to guide county planning and adaptation funding.