It's part of the duality of our world. Flowers can't bloom without rain after all. If you want the spiritual and not scientific answer the Lord and Lady have a light and dark side as we all do. Most Wiccans prefer to associate with the light side over the dark side, but you can call on the God and Goddess for negative reasons [example, someone attacked a loved one and you want revenge] so natural disasters could be seen as the Gods anger, or perhaps they're in a bad mood. You could also look at it as the Goddess or God playing with the powers [similar to how many new pagans cast spells for many random things to see what happens]
The Lady and Lord however don't hate us, they are our parents who watch over, but the divine is everywhere and inside everything [including us] that's the thing about the Wiccan God and Goddess, they're not perfect. There is no all good and all bad deity. You need to look at natural disasters and find a lesson or silver lining.
Course, the scientific answer is that's a part of nature due to various pressure systems and fault lines which cause the various types of disasters. While I believe in the science, I feel it's part of life, light and darkness need to coexist, so there will be ups and downs, it's life. Its not the Gods fault, you shouldn't blame them, just as you wouldn't blame your parents if you crashed your car. They'll be there to help and support you, not keep you safe from everything.