Introduction.—Storm Klaus swept through southwestern France on Saturday, January 24, 2009, leaving more than 1.7 million households without power, including 477,000 in the Midi-Pyrénées region. The objective of this study is to assess the storm’s impact on carbon monoxide (CO) poisoning based on emergency department activity in Midi-Pyrénées. Method: Since 2005, the Midi-Pyrénées Regional Emergency Observatory has collected medical and administrative data daily for each emergency department visit; visits for CO poisoning during the 2009 storm period could be compared to the equivalent period in 2008 by month (January), week (W3-W4-W5), day (Saturday, Sunday), and time of admission. Results.—While 37 cases were recorded in January 2008, 156 were recorded in January 2009 (p < 0.0001), nearly three-quarters (109) of which occurred starting on Saturday the 24th, exclusively from Haute-Garonne (61%), Tarn (24%), Tarn-et-Garonne (11%), and Gers (4%). The first three days following the storm accounted for 81% of poisonings, with Saturday accounting for 85% between 3:00 PM and 6:00 PM, and Sunday showing two distinct peaks between 12:00 AM and 4:00 AM and 8:00 PM and 11:00 PM. The median age of patients poisoned after the storm was 28 years [Q1: 13; Q3: 44] compared with 34 years [Q1: 21; Q3: 60] before the storm (p = 0.07). The male-to-female ratio was 1.02 and did not differ by period of poisoning (p = 0.95). Discussion/Conclusion.—We do not have data on the mechanism of CO exposure in this cohort, but various studies have shown in similar situations that the primary source was the inappropriate use of generators. These results highlight the need to inform the public about the risks associated with the use of these devices, which are increasingly used by individuals during power outages. A cross-sectional analysis with a time-stratified matching design could be considered to control for temporal factors. (R.A.)