Potato cyst nematodes (PCN) are economically important pests of potato plants worldwide that can result in yield losses exceeding 80% and which has been estimated to cost £50m annually in the UK alone. The life cycle of PCN, and in particular the hatching of eggs and development and survival of juveniles, is sensitive to temperatures in the soil. Despite this fact relatively little is known about temperatures inside potato drills and how these may differ to temperatures in the surrounding soil. We monitored the temperature inside potato drills at 19 sites across the UK and used a published temperature-driven process-based PCN life cycle model to compare predictions of PCN population dynamics driven by these temperatures to predictions based on modelled soil temperatures derived from the HadUK-Grid climate. We found that mean soil temperatures derived from the climate model were lower than those observed inside potato drills, which resulted in increased estimates of population growth and shorter estimated generation times when using temperatures measured directly in potato drills than when using modelled soil temperatures. This finding suggests that greater understanding of the temperature inside potato drills is required if we are to make accurate predictions about the effects of increased temperatures under climate change on PCN populations.