Asthma is one of the numerous syndromic indicators daily monitored at the regional and national levels by the French syndromic surveillance system based on the emergency departments Oscour network. This indicator presents important daily fluctuations and can be influenced by several environmental, infectious and societal factors. Particularly the short-term impact on asthma of episodes like the air pollution peak experienced in March 2014 and the thunderstorm occurred in July 2014 has been analysed by age group on the Paris area, as well as the effect intrinsic factors (day-of-week, seasonal period, holidays).