<p>Literature has evidenced that climate change is reflected in youth everyday life, but little is known about this subjective experience. We explore in what ways do Portuguese adolescents and emerging adults mention climate change in their reflections on daily life without being prompted to do so. Considering the participants who mentioned climate-related issues, we further explored whether thinking about civic engagement is associated with negative or positive affect and the potential moderator role of Positive Youth Development. Data were collected from 110 participants (16–24, 80.9% women, mean age = 20.12; SD = 1.90) over seven days (a complete week) using the Experience Sampling Method (3944 moments). Nine participants mentioned climate change in their daily life, mainly in their thoughts. Multilevel regression analysis showed no significant association between the thoughts of the participants who mentioned climate related issues and positive and negative affect. However, by introducing Positive Youth Development as a moderator in the association between these participants’ thoughts and negative affect, we observed a decrease in negative affect, when thinking about civic engagement was compared with thinking about other issues. Findings show that an ecological approach is essential to comprehend how climate change manifests in adolescents and emerging adults’ daily life. Recommendations are provided for future ESM studies in this field of research. Further studies are needed to understand the influence of reflections on climate-related issues in youth levels of affect across daily life and explore the role of Positive Youth Development in balancing positive and negative affect within climate change issues.</p>