Pseudo-Bartter syndrome (PBS) describes an uncommon but well recognised complication of cystic fibrosis leading to hypochloraemic, hypokalaemic metabolic alkalosis. Pseudo-Bartter syndrome is usually seen at initial presentation or within the first two years of life in children with cystic fibrosis. Risk factors for development of PBS include warm weather conditions, severe respiratory or pancreatic disease and gastrointestinal losses (e.g. vomiting and diarrhoea). PBS is rare in older children and adolescents although epidemics have been associated with heat wave conditions in warmer climates. In this era of climate change, it is crucial that clinicians consider Pseudo-Bartter syndrome when patients with cystic fibrosis present unwell during summer.