IEC 60721-3-3:2019 classifies groups of environmental parameters and their severities to which products are subjected when installed for stationary use at weatherprotected locations.This third edition cancels and replaces the second edition published in 1994, Amendment 1: 1995 and Amendment 2:1996. This edition constitutes a technical revision.This edition includes the following significant technical changes with respect to the previous edition:a) Clause 3: definitions aligned with IEC 60721-3-1.b) Clause 4: aligned with IEC 60721-3-1.c) Clause 5: Clause A.3 has been incorporated into Clause 5.d) Subclause 5.2: all existing climate classes have been replaced by completely new classes. The new classes are divided into two groups. The reason for the new classes is the latest revision of IEC 60721-2-1 which incorporates new climate types.e) Subclause 5.3: addition of a new class for low air pressure.f) Defined values of chemically active substances are now by reference to ISO 9223.g) Subclause 5.6: all existing classes for mechanically active substances have been replaced by completely new classes, in alignment with IEC 60721-3-1.h) Subclause 5.7: all existing classes for mechanical conditions have been replaced by completely new classes, in alignment with IEC 60721-3-1.i) Table 1: new climatic classes with new severities.j) Table 2: new class for low air pressure.k) Table 4: new mechanically active substances classes.l) Table 5: new mechanical conditions classes.m) Annex A: revised and includes a clean climatogram.n) Annex B: revised and includes the definition of seismic environment.o) All classes regarding fire, all combined classes, all chemically active substances classes, Clause A.2, Annexes C, D and E have been removed.