Tonight at 6:56pm EDT, United Launch Alliance's Delta IV rocket will launch from Launch Complex 37 in Cape Canaveral, FL, carrying the WGS-10 satellite into a Geostationary Transfer Orbit.
The launch window for tonight's launch is open until 9:05pm EDT, giving them roughly 2 hours to solve any technical issues on the rocket if they come up prior to liftoff. Weather conditions throughout the window show an 80% chance of favorable weather with a chance of some isolated showers at the beginning of the launch window. Weather conditions worsen to 60% favorable in case of a 24-hour delay.
This Delta IV is the last one to launch in this specific configuration, with 4 strap-on solid rocket boosters provided by Northrup Grumman and a 5 meter wide payload fairing. There is one more "single stick" Delta IV after this targeting a launch in July, which will be the last one to launch. After that launch, the rest of the Delta launchers will be the Delta Heavy, which will then retire in 2022. Both Delta and Atlas will slowly be phased out and replaced with their new Vulcan rocket, which has a maiden launch of April 2021.