To understand the spatiotemporal evolution of online public opinion and reveal its formation mechanism, we investigate the data from several popular online comments by means of statistical physics. Although the empirical results show that the heterogeneity of concerns exists in different areas, which follows a double power law, an obvious consistency of such concerns occurs during the evolution of online public opinion. Through correlation analysis, we reveal that the regional population and economy may have a significant influence on the concern about the event, and find that the consistency of concerns in different areas derives from the strong correlations among regions. On the other hand, the public opinion guide can significantly affect the concern about the event, and lead to the rapid increase of propagation velocity. By calculating the information entropy of propagation velocity, we find that the geographical distribution of online comments is relatively stable in most time, and the public opinion guide may help to maintain this consistency. Furthermore, the correlation analysis shows that the more developed areas tend to be more synchronized, which suggests the responses of these areas to the public opinion guide may be faster. Therefore, enhancing the guide of public opinion in developed areas can help our government to control the spread of the online public opinion.