Artemis l: Rain, lightning will be a concern heading into NASA's historic moon rocket launch

Before NASA's Space Launch System rocket launches, sending the uncrewed Orion spacecraft on a 42-day mission around the moon, all eyes will be on the forecast for Florida's Space Coast.

Four days before the SLS is slated to blast off with 8.8 million pounds of thrust, launch forecasters with the 45th Weather Squadron are predicting a 70% chance of favorable weather for the Artemis 1 liftoff. The two-hour launch window opens at 8:33 a.m. ET on Monday, Aug. 29.

It is summer in Florida, and the primary concerns will be any storms that roll in, creating cumulus cloud coverage, rain and lightning. The SLS can only launch under specific weather criteria, including constraints regarding temperature, wind, rain, cloud cover and lightning. 

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"While the overall lightning threat seems low, this onshore flow regime will promote scattered showers across the Atlantic waters through the launch window," Launch Weather officers wrote. "As a result, the primary weather concerns for a Monday morning attempt will be the Cumulus Cloud Rule, Surface Electric Fields Rule, and the Flight Through Precipitation constraint."

The 322-foot-tall rocket requires more than 700,000 gallons of cryogenic fuel. Teams will not begin tanking the rocket with fuel if the temperature is more than 94.5 degrees Fahrenheit above 132.5 feet. Tanking cannot start under 41.4 degrees, but that won't be a problem for this August launch window.

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The SLS cannot launch through rain, and liftoff will be delayed if winds are between 29 and 39 knots (33 and 44 mph) above 132.5 feet. 

Upper-level winds are also a factor. The rocket will not launch if mission managers believe winds could create a problem for the launch vehicle during ascent. 

Cumulus cloud cover within a 10 nautical mile range could also delay the launch, depending on the clouds' type, distance and height. The launch director will not allow the countdown to continue if the SLS flight path is within 3 nautical miles of a thunderstorm debris cloud.

The launch complex must also be lightning-free for 30 minutes after lightning within 10 nautical miles is observed. 

Lightning near the Kennedy Space Center delayed the SLS rollout to the launchpad last week. After it cleared, teams completed the 4-mile journey to launchpad 39B.

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Peak hurricane season is approaching, and the FOX Forecast Center continues to monitor anything that might alter or delay the launch. 

A couple of tropical disturbances in the Atlantic Basin are worth watching for possible development into the weekend.

These disturbances aren't likely to create problems for Monday's launch window. However, if the launch delays to either backup opportunities on Sept. 2 or Sept. 5, the tropical activity is worth watching.

This story will be updated with new forecasts daily leading up to the Aug. 29 Artemis 1 launch. 

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