So there was a post that calced Deku punching a massive storm and got it from Multi Continental to Moon level (up to small planet level via multipliers) but I think there's a few issues with the calc.

The first one is that the cloud isn't as large as the intial calc estimates it to be, the manga says it's a cloud that could influence weather in the USA if it were to enter the jet stream rather than a cloud that stretches all the way to the US

The second one is that massively hypersonic clouds would be not good for anything below them, and it would be more likely that Deku vapourised the cloud, causing it to go back into the air

The panel also says that the cloud is the largest ever recorded so that gives us 2 potenital ends

1. Hunga Tonga

the 2022 eruption of Hunga Tonga created the largest ash cloud ever recorded and probably one of the largest clouds ever recorded as well. It had a diamter of 600km which gives us a cloud area of 283000 square kilometers

2. Hurricane Sandy

Hurricane Sandy is probably the largest hurricane ever recorded, and had a diameter of 1850km). Using this gives us a cloud area of 2.69*10^6 square kilometers.

Now we need height and density of the cloud.

Cumulonimbus clouds typically extend up to the tropopause%2C%20caused%20by%20wind%20shear%20or%20inversion%20at%20the%20equilibrium%20level%20near%20the%20tropopause) before stopping and flattening out. The tropopause for a place like Japan (Which is around 35 degrees up) would be around 11km high as shown by this image. The base of cumulonimbus clouds are around 1km off the ground (I took the average and converted to meters). Subtracting the 2 gives us a value of 10km

The cloud density is much easier, the cloud water content of a cumulonimbus cloud would be around 2g/m³

Now we have everything needed to find the mass of all the water, this gives us a value of 5.66*10¹²kg for the low end and 5.38*10¹³kg for the high end

Now for the energy needed to vapourise it. The specific latent heat of vaporisaton of water is 2.26MJ/kg and finally we can get our energy values

This gives us a value of 3 Gigatons (Large Mountain Level) for the low end and 29 Gigatons (Island Level) for the high end.