(CNN)It's a moment that hasn't happened in nearly a decade, and it might all come down to the weather.
According to the official weather forecast from the US Air Force 45th Weather Squadron, there's only 50% chance of favorable conditions for a "go."
That is a drop from Tuesday's 60% chance for liftoff.
The forecast is the same odds as a coin flip now.
The SpaceX Falcon 9 rocket is planned to launch from Kennedy Space Center in Florida on Wednesday at 4:33 p.m. ET -- the first manned rocket launch from the US in nearly a decade.
After record rainfall in Florida this week, there's a decent chance we might have to wait even longer.
Some forecast models are hinting at a break in the showers during the afternoon while others put storms right near the launch site.
There will definitely be hit-or-miss showers and storms in the vicinity of the launch pad. Florida typically gets "pop-up" storms during this time of year. They are incredibly difficult to predict where they will emerge -- it is kind of like predicting where a bubble will form on the top of boiling water.
The forecast does call for showers and storms in the afternoon, so a scrub due to weather is possible.
Launch or scrub
A whole team of meteorologists will be on hand from the 45th Space Wing and SpaceX to determine whether the weather will scrub the launch. The decision can be made right up to liftoff.
According to NASA, certain types of conditions can scrub a launch.
For example, if there is lightning in the area, that will cancel a flight. Forecasters have to monitor the winds. If there is a sustained wind of 30 mph or more 162 feet above the launch pad, the mission will be canceled.
Florida has had torrential rain from a tropical disturbance for the last several days, bringing flooding rain to the east coast of the Sunshine State.
In parts of South Florida, rain fell at a rate of 4 inches per hour. Along with the rain, came tornado warnings and winds gusting as high as 55 mph.
Earlier this month, NASA had to delay its launch of the Atlas V rocket, US Space Force mission due to Tropical Storm Arthur. It launched the following day after the storm cleared out.
If the weather hampers Wednesday's launch, the next available launch windows are at 3:22 p.m. ET Saturday and Sunday at 3 p.m ET.