StayCool is a portable, solar-powered evaporative cooling system designed to reduce extreme heat buildup inside parked vehicles [1]. The system addresses a critical comfort and safety issue, especially in hot climates where children, pets, and drivers are at risk of heatstroke [2]. It uses a Nordic nRF52840 microcontroller with temperature, humidity, and water level sensors to determine when to activate an onboard fan and misting system. Real-time data is sent to Firebase via an LTE Cat M1 modem, allowing users to monitor and control the system remotely through a mobile app. Experiments confirmed the cooling system reliably activates at threshold temperatures and that cloud-based data synchronization remains fast in most conditions [3]. Challenges like water usage, power availability, and network latency were identified and addressed through hardware safeguards and app integration. Ultimately, StayCool demonstrates a smart, autonomous, and energy-ef icient approach to keeping vehicle interiors safe and comfortable.