Cohesion is an important part of effective team performance. Previous research has focussed on cross-sectional self-report measures in business settings. However, in extreme environments where contextual factors (e.g., weather conditions) can vary considerably from day to day, micro-variations in cohesion could influence daily performance. In small teams under pressure, such variations may be moderated by personality traits. The current study presents a diary methodology to explore variation in cohesion in five expedition teams – tracking temporal changes in cohesion and daily events over twenty days. Pre-expedition personality measures were used to explore the impact of team composition on variations in cohesion. Findings demonstrated that events significantly predicted fluctuations in cohesion across teams. Having more extraverted team members had a negative impact on cohesion. These results offer valuable insight to how this method can track changes in cohesion over time and subsequently enhance understanding of how to mitigate cohesion breakdowns.