Is it illegal to cheat in weather forecast?

You really don't understand. National weather forecast serves the people. If there is any deviation, you can question its authority, but it belongs to the nature of national service. It is not feasible to sue the weather forecast. However, if you have evidence that it is caused by negligence and intentional prediction research, you can sue the relevant departments and ask them to apologize to the people. If great economic losses are caused, you can also claim compensation. Furthermore, as an individual, if the weather is reported in front of people, if it has a great negative impact, there will be drunkards who disturb social order. If your "cheating" also refers to other aspects of fraud, it's not illegal.