Today's #LaunchAmerica DM-2 flight for @NASA and @SpaceX was scrubbed due to three weather violations:

-Lightning rule
-Anvil cloud rule
-Field mill rule

So...what are these three violations? How can weather prevent something as advanced as a rocket from flying?

The lightning rule is fairly straightforward. You don't want your rocket lifting off when lightning is nearby. Rockets and spacecraft contain sensitive electronics, and propellant, well...you get the idea. It's a bad idea, don't launch with lightning around.

The anvil cloud rule also deals with lightning, as especially potent thunderstorms generate anvil head clouds. They also can have powerful winds that could jeopardize a rocket's ability to control itself, and ice crystals that could damage surfaces and systems.

The field mill rule requires some explanation: @NASA has sensors around @NASAKennedy that measure electrical fields in the atmosphere. Rocket exhaust is a weak plasma, basically a highly-charged gas, so if you get the right charge combo, your rocket can make its own lightning.

Rockets have been hit in flight by lightning before! Apollo 12's Saturn V was struck twice on launch in 1969. Ascending in the middle of a rainstorm, the ionized exhaust plume allowed a discharge to zap through the rocket and down to the pad, almost ending the mission.

Just last year a Russian Soyuz rocket was struck by lightning in flight, although it didn't seem to notice.