What a fun assignment! As king and queen of the fairies, both Oberon and Titania possess great powers. When they argue, the powers they have are displayed in ways that greatly affect conditions around them, including the weather. Titania describes the results:

Therefore the winds, piping to us in vain,
As in revenge, have suck'd up from the sea
Contagious fogs; which falling in the land
Have every pelting river made so proud
That they have overborne their continents:

Winds blowing in from the ocean cause fog over the land. Tremendous rains cause rivers to flood, destroying farms near and far. The seasons themselves seem to get mixed up:

the spring, the summer,
The childing autumn, angry winter, change
Their wonted liveries, and the mazed world,
By their increase, now knows not which is which:

Your weather report would include information about all these amazing and possibly frightening events. You should include data about how much rain fell over a given period of time, the estimates of the cost to repair the flood damages, and perhaps an interview with someone whose livestock was swept away by the rampaging river. If you can use visual aids with your report, pictures of spring flowers coated in ice would be very appropriate.