Leather jackets can be worn in warmer weather, but it largely depends on the thickness of the leather and the style of the jacket. Some leather jackets are designed with lighter-weight leather or perforations to help with breathability and ventilation, making them suitable for wearing in warmer weather. However, heavier leather jackets are typically designed for colder weather as they can be too warm and uncomfortable in hot weather.
Another factor to consider when wearing a leather jacket in warmer weather is what you pair it with. Wearing a leather jacket with a lightweight t-shirt or a breathable fabric can help to keep you comfortable and cool.
Overall, if you choose a lighter-weight leather jacket with ventilation, and wear it with appropriate clothing, you can wear real leather jackets for men in warmer weather. However, it's important to be mindful of the weather and your own comfort levels, as leather jackets are typically designed for colder weather.