Enlarge / Weather conditions at Kennedy Space Center are not great this week. (credit: Trevor Mahlmann)

Now that humans are about to lift off from the United States into orbit again, the constraints surrounding launch weather are heightened. To that end, we’re watching conditions closely today in advance of a historic launch of a Falcon 9 rocket and Crew Dragon spacecraft at 4:33pm ET (20:33 UTC).

This will be the first launch of humans into orbit from the United States since the space shuttle retired in 2011, and people who remember that program will recall plenty of scrubs. For today’s launch, we need to watch conditions both at the launch site and down range to monitor for any emergencies with the rocket during the countdown or after it launches.

Launch site weather

For Kennedy Space Center and SpaceX’s Launch Complex 39A, there are 12 different criteria near the pad that must be met before a launch can proceed. These include sustained winds of 30mph or below, no anvil thunderstorm clouds within 10 nautical miles, and various rules about clouds.