A fast and accurate determination of voltage stability weak areas allows the power system operator to execute preventive actions, aimed to maintain an adequate operation under changing conditions. However, due to the large number of possible power system operating conditions, the determination of weak areas becomes a challenging task.This paper is oriented to discuss an approach for online identification of these areas in the power system, where exist a high risk of experience voltage stability problems. The proposal, which is part of a situational awareness tool, initially defines the weak voltage stability areas and next determines the actual voltage stability weak area, using the measurements obtained from the power system. According to the tests performed in two power systems (IEEE 14 and 30 nodes), the proposed alternative has high performance rates on the online identification of voltage weak areas. The obtained errors are lower than 1% in more than 111,000 different operating conditions of the analysed power systems. The high performance of the proposed strategy, validate its use as a part of a situational awareness tool.