Calc Adventure Time - Ice King vs Flame Princess

0:35
Flame Princess and the Ice King bring storm clouds into their battle that span all the way to the Candy Kingdom. Note when we see Finn looking to the Ice King, we see no clouds following him and the clouds stop moving when they clash. According to the IOS game Jumping Finn (it's the best I have to go with) the Ice Kings Mountain is 9km from the treehouse.
204 pixels = 9km
1 pixel = 9km/204 = 0.0441176471km
0.0441176471km X 284 = 12.5294118km (12529.4118m)

Nimbostratus clouds are dark clouds, and can produce snow which is in line with the Ice Kings powers, so I'll be going with that. Nimbostratus clouds usually have a thickness of at least 2000m up to 4000m. Volume as a cylinder.

(Low end)

V = πr^2h
= π X 12529.4118^2 X 2000
= 9.86373134e11m^3

Density of a cloud is 1.003kg/m^3.

M = 9.86373134e11 X 1.003
= 989332253402kg

(High end)

V = πr^2h
= π X 12529.4118^2 X 4000
= 1.97274627e12m^3

M = 1.97274627e12 X 1.003
= 1978664508810kg

Now for the timeframe.
1.51 seconds.

T = 12529.4118m/1.51s
= 8297.62371m/s

(Low end)

E = (0.5) X 989332253402 X 8297.62371^2
= 3.40580395e19 joules
= 8.1400668021032505095 gigatons

(High end)

E = (0.5) X 1978664508810 X 8297.62371^2
= 6.8116079e19 joules
= 16.280133604206501019 gigatons

Final Results
Ice King & Flame Princess create a storm (low end) = 8.140 gigatons
Ice King & Flame Princess create a storm (high end) = 16.280 gigatons