Mobile context-awareness becomes an important research topic since mobile information browsing is still difficult due to the limitations of mobile devices. On the other hand, it is easier to gather more user contexts because mobile devices are equipped with more sensors. In this paper, we introduce a method for detecting local hot topics from microblogs on a mobile device. In order to detect user-related topics from microblogs, it exploits mobile user contexts such as location, activity, blogging history and social relationship. Through taking advantage of these contexts, it retrieves user-related microblogs and also infers user interests. It can filter out unrelated topics based on the inferred interests. Based on our proposed method, a mobile user can be aware of topics related to interests surrounding the user.