Yes, you can absolutely use a window air conditioner in your room when it's hot outside and not at night. Window air conditioners are designed to cool a specific area, such as a single room, and can be a practical solution to maintain a comfortable indoor temperature during hot weather.
Using the air conditioner during the hottest parts of the day can help you stay cool and comfortable while you're in the room. When the outdoor temperature drops in the evening or at night, and you no longer need the air conditioning, you can turn it off or set it to a higher temperature to save energy and reduce electricity costs.
It's important to note that running an air conditioner continuously can increase your energy consumption and utility bills. If you want to be more energy-efficient, consider using the air conditioner in conjunction with other cooling methods, such as fans, shading your windows, and keeping doors closed to retain cooler air. Regular maintenance of your air conditioner, such as cleaning the filters, can also help it run more efficiently.
Remember to follow the manufacturer's guidelines and safety recommendations when installing and operating your window air conditioner to ensure proper usage and avoid any potential hazards.