The change to the beginning time of the race comes after the earlier two scheduled grands prix, in Bahrain and Saudi Arabia, have been cancelled due to the battle within the Center East.
The choice was made by business rights holder F1 and governing physique the FIA on Saturday night in Miami.
An announcement from F1 and the FIA stated it was made as a result of “the climate forecast (predicts) heavier rainstorms later within the afternoon near the unique deliberate race begin time”.
The assertion added: “This choice has been taken to make sure the least quantity of disruption to the race, and to make sure the utmost doable window to finish the grand prix in the perfect circumstances and to prioritise the protection of drivers, followers, groups and workers.”
The goal is to attempt to end the race earlier than the worst of the climate arrives, which is forecast to be at about 15:00 native time (20:00 BST), one hour earlier than the unique begin time.
That heavy rain, as soon as it begins, is anticipated to remain for hours, so the worry was that sticking with the unique begin time would have meant the race couldn’t be run.
Native legal guidelines within the US imply that the race may very well be suspended if there’s a risk of a lightning strike at or across the circuit. This might be to permit all personnel to “shelter in place”.
A collection of protocols have been introduced by the FIA defining how that may be administered both earlier than or through the race.
Shifting it ahead, the race continues to be more likely to be moist, however the hope is the circumstances might be acceptable for working the vehicles.
F1 vehicles do run within the rain, however the limiting issue is all the time visibility from the huge quantities of spray thrown up by the vehicles, in addition to aquaplaning if the quantities of standing water are vital sufficient to pressure the low-running vehicles to successfully float on high of water on the observe.
Norris’ team-mate Oscar Piastri added: “It is clearly going to be a voyage into the unknown for everyone. When it rains right here, it usually is fairly torrential, so it may very well be an attention-grabbing day.
“It is simply going to be what occurs with the power-unit, the way you get energy, the place you get energy is in a pc’s arms.
“Simply ensuring that that does roughly what we count on. Clearly, the margin for error when it is moist is considerably smaller.”
