Calculate chill hours for fruit trees to ensure proper dormancy and flowering. Use standard, Utah, or dynamic models.
You might also find these calculators useful
Calculate heat units for crop growth and development
Convert between Celsius, Fahrenheit, and Kelvin
Calculate plants or seeds needed for any field size
Calculate fertilizer rates based on NPK requirements
Chill hours are the accumulated hours of cold temperatures (typically 32-45°F) that deciduous fruit trees and perennial plants need during winter dormancy. Proper chill accumulation is essential for healthy bud break, flowering, and fruit production in spring.
Chill hours represent the time trees spend within a specific cold temperature range during dormancy. This cold exposure triggers hormonal changes that allow trees to break dormancy and produce fruit. Different fruit varieties have different chill hour requirements, making location and variety selection critical for successful orchards.
Standard Chill Hours Formula
CH = Σ hours where 32°F ≤ T ≤ 45°FChoose fruit tree varieties suited to your region's typical chill accumulation.
Estimate when trees will break dormancy and begin flowering.
Identify years with insufficient chill that may affect fruit production.
Most apple varieties need 800-1200 chill hours for proper fruiting.
Peaches, cherries, and plums have varying chill requirements (300-1000 hours).
Evaluate locations for new orchard establishment.
Monitor winter progress and predict spring growth timing.
Trees may experience delayed or irregular bud break, reduced fruit set, poor fruit quality, and extended bloom periods that increase frost damage risk.