Why This Matters ▼
Rothamsted hosts the longest continuous daily met record in the UK (since 1853). Warming has been ~1.2°C. For winter wheat, heat stress around anthesis (flowering, late May-mid June) and during grain filling (June-July) is the most dangerous climatic bottleneck.
Temperatures exceeding 25-27°C cause pollen sterility. Warmer temperatures also shorten the grain-filling duration, leading to smaller, lighter grains and significantly reducing overall yield.
Temperature Impact on Grain Weight
Post-anthesis mean temperature (June-July mean °C) vs. Thousand Grain Weight proxy (g).
Temperature Danger Zones
<20°C
Safe zone for grain fill
20-25°C
Moderate stress, shorter fill duration
>25°C
Severe: pollen sterility risk
>30°C
Extreme: enzymatic breakdown
Heat Day Frequency (June-July)
Annual Mean Temperature Trend
Methodology & References ▼
- Thorne et al. (1988) - Grain growth of winter wheat in response to temperature.
- Senapati & Semenov (2021/2022) - Impact of heat stress on wheat yields and projections.
- Harkness et al. (2020) - Long-term weather records at Rothamsted.