Everyday is a choice to be in a science fair.
You don’t have to wait for someone to organize an event, choose the judges for it and wait for others to participate. You can choose to do something interesting, and then show it to a bunch of people who would be interested to learn more about what you are studying.
Science no longer has events and gatekeepers holding it back. It actually never did, regardless of how much it felt that way. There was always an opportunity to sidestep the whole process, but it was much harder to find the names of people who might be interested. LinkedIn and other similar sites have made this much easier.
There isn’t a reason to wait to organize a project unless you need time to clarify in your mind what the problem is, who should be involved and what is necessary to get started. If you have that, now is as good a time as any to get going.