BACKGROUND The occurrence of cold temperature-related symptoms has not been investigated previously in young adults, although cold weather may provoke severe symptoms leading to activity limitations, and those with pre-existing respiratory conditions may form a susceptible group. We tested the hypothesis that young adults with asthma and allergic rhinitis experience cold-related respiratory symptoms more commonly than young adults in general. METHODS A population-based study of 1623 subjects 20-27 years old was conducted with a questionnaire inquiring about cold weather-related respiratory symptoms, doctor-diagnosed asthma and rhinitis, and lifestyle and environmental exposures. RESULTS Current asthma increased the risk of all cold weather-related symptoms (shortness of breath adjusted PR 4.53, 95% confidence interval 2.93-6.99, wheezing 10.70, 5.38-21.29, phlegm production 2.51, 1.37-4.62, cough 3.41, 1.97-5.87 and chest pain 2.53, 0.82-7.79). Allergic rhinitis had additional effect especially on shortness of breath (7.16, 5.30-9.67) and wheezing (13.05, 7.75-22.00), some on phlegm production (3.69, 2.49-5.47), but marginal effect on cough and chest pain. INTERPRETATION Our study shows that already in young adulthood those with asthma, and especially those with coexisting allergic rhinitis, experience substantially more cold temperature-related respiratory symptoms than healthy young adults. Hence, young adults with a respiratory disease form a susceptible group that needs special care and guidance for coping with cold weather.