IEC 62793:2020(E) describes the characteristics of thunderstorm warning systems (TWSs) in order to implement lightning hazard preventive measures. Single sensors and/or a network of sensors (e.g. lightning location system) can be used as a TWS. This second edition cancels and replaces the first edition, published in 2016. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - portable devices are no longer covered by this standard; - in Clause 5, classes of TWS have been deleted; - in Clause 6, updated figures and more detailed text are provided to better illustrate the alarm timeline; - in Clause 9, the text has been summarized and refers now to the application guide given in Annex F; - annexes have been reorganized; - Annex E is normative.