There are several situations where you can consider launching an impromptu rally: 1. **Emergency**: When a major social event, political change or natural disaster occurs, the public may need to communicate and organize immediately to express their demands or provide support. 2. **Emergency protest**: If a policy, law or action causes widespread dissatisfaction and requires a quick response, you can consider organizing a rally quickly. 3. **Topics of public concern**: When some issues suddenly attract widespread public attention, such as environmental protection, social justice, human rights issues, etc., you can launch an impromptu rally to focus on discussion and action. 4. **Celebration**: After some sudden positive events (such as victory in sports events, success in cultural events, etc.), people may spontaneously gather to celebrate. 5. **Community needs**: When urgent problems arise in the community (such as safety hazards, damage to public facilities, etc.), residents may need to gather to discuss response measures. 6. **Online mobilization**: When people discuss a certain issue on platforms such as social media, if the response is positive, you can quickly organize an offline rally. When considering launching a rally, you should ensure that you comply with relevant laws and regulations to protect the safety and interests of participants.