Although the UK has been relatively spared significant geophysical impacts of climate change, many people, youth in particular, are increasingly worried about climate change. The psychological distress associated with the (perceived) threat of climate change has been linked to poorer mental wellbeing but can also promote adaptive responses such as engagement in pro-environmental behaviour. In this mixed methods study, we delve deeper into the experience of 'climate distress' among UK residents aged 16-24 (N = 539). We conducted an online survey assessing general mental health, subjective wellbeing, and climate distress with existing scales. We also included novel questions assessing positive and negative life impacts of climate change, open-ended questions on aspirations and priorities for the future, and engagement in pro-environmental and climate actions. Our findings indicate that mental health factors may contribute to vulnerability to climate distress. Predictably, socio-psychological responses to climate change (i.e., frustration over inaction, lack of control, and shame or guilt about one's own contributions) were linked to higher scores on the climate distress scale. Negatively appraised climate change-related events (i.e., seeing an environment they care about change for the worse) were associated with higher climate distress. Individuals with high climate distress (10.1% of our sample) reported worrying about the impact of climate change on their own future more frequently than any other topic surveyed (including personal finance, career, relationships, politics). Both positive (hope/interest) and negative (anger/frustration) emotions inspired action-taking, especially climate activism, which was negatively predicted by guilt/shame and sadness/fear. Private-sphere pro-environmental actions appeared less driven by strong emotions. Overall, our findings present a more nuanced picture of climate distress in terms of emotional responses, behaviour, and mental health. Longitudinal research is urgently needed to understand how distress may change over time, and the conditions that lead to adaptive and maladaptive outcomes.