Instead of scaling manually, you might want to Scale-Up your fleet proactively for the given duration. This is a possibility if you have an Auto Scaling Group. You can schedule an action for the given date and time to increase or decrease the fleet size. This can be done using Write-ASScheduledUpdateGroupAction.
PS C:\> Write-ASScheduledUpdateGroupAction -AutoScalingGroupName WebAppASG -ScheduledActionName "MyWebAppScheduleActionUp" -StartTime "2017-07-10T12:06:00Z" -DesiredCapacity 4
In this example, the Auto Scaling Group fleet size is scheduled to increase to the desired capacity of 4 on 10-Jul-2017 at 12:06 PM GMT/UTC. Note that, you have to always specify the time in GMT/UTC. If you feel that you require this fleet size just for an hour, you can schedule the Scale-In an action as per the following:
PS C:\> Write-ASScheduledUpdateGroupAction...