Quantum Key Distribution (QKD) is increasingly considered for metropolitan critical communications, yet most operational evidence is derived from temperate regions. In tropical countries such as Malaysia, persistent high humidity, intense rainfall, and seasonal monsoon cycles introduce distinct challenges for metro fiber networks, including water ingress, connector contamination, temperature-driven polarization drift, and increased maintenance interventions. This paper investigates the performance, reliability, and climate sensitivity of QKD over tropical metropolitan fiber corridors. A climate-aware evaluation framework is developed, linking environmental stressors to measurable QKD metrics such as secret key rate (SKR), quantum bit error rate (QBER), and key service availability. Representative metro scenarios demonstrate that monsoon-related disturbances can significantly degrade SKR and availability if unmanaged, particularly near operational distance limits. Results further show that adaptive stabilization, enhanced optical hygiene, key buffering, and season-aware operational policies can effectively mitigate climate-induced degradation. The study provides practical engineering guidance for deploying reliable, high-availability QKD systems in tropical metropolitan environments.

Quantum Key Distribution (QKD);artificial intelligence;communications;process innovation