Thought to be legacy code from some sort of never-implemented weather controlling system, the power that suffuses an Arc Caster allows them to manipulate humidity, pressure, and wind speed - and even generate powerful electrostatic charges. These source coders have an instinctive understanding of the weather around them, and of the forces that produce that weather.
Weather Forecast
You have an intuitive knowledge of the current and upcoming weather. You can always sense the air temperature, humidity, and current weather conditions within one mile of you, even if you are underground or indoors. You can also determine the weather a number of days into the future equal to your proficiency bonus + your Charisma modifier (minimum of one day). This forecast is perfectly accurate, short of being altered or manipulated by techs or similar special powers.
Tempest Tossed
Starting at 1st level, you can use a bonus action on your turn to cause whirling gusts of air to briefly surround you, immediately before or after you cast a tech of 1st level or higher. Doing so allows you to fly up to 10 feet without provoking opportunity attacks.
Tempest Hardened
At 6th level, you gain resistance to lightning and thunder damage. In addition, whenever you start casting a tech of 1st level or higher that deals lightning or thunder damage, electrostatic power erupts from you. This eruption causes creatures of your choice that you can see within 10 feet of you to take lightning or thunder damage (choose each time this ability activates) equal to half your source coder level.
Storm Guide
At 6th level, you gain the ability to subtly control the weather around you.
If it is raining, you can use an action to cause the rain to stop falling in a 20-foot-radius sphere centered on you. You can end this effect as a bonus action.
If it is windy, you can use a bonus action each round to choose the direction that the wind blows in a 100-foot-radius sphere centered on you. The wind blows in that direction until the end of your next turn. This feature doesn't alter the speed of the wind.
Storm's Fury
Starting at 14th level, when you are hit by a melee attack, you can use your reaction to deal lightning damage to the attacker. The damage equals your source coder level. The attacker must also make a Strength saving throw against your source coder tech save DC. On a failed save, the attacker is pushed in a straight line up to 20 feet away from you.
Wind Waker
At 18th level, you gain immunity to lightning and thunder damage.
You also gain a flying speed of 60 feet. As an action, you can reduce your flying speed to 30 feet for 1 hour and choose a number of creatures within 30 feet of you equal to 3 + your Charisma modifier. The chosen creatures gain a flying speed of 30 feet for 1 hour. Once you reduce your flying speed in this way, you can't do so again until you finish a short or long rest.