Answer: Check Explanation Below ;)
Step-by-step explanation:
Seattle is a very rainy city just like many others in the Pacific Northwest region.
Now, you can't be absolutely sure how rainy it would it would be the next year, but judging by the experimental probability of the 30 years, the rainfall of more than 15 inches would be 100%.
That may not be the actual likeliness of a more than 15 inch rainfall, but with no additional data, that's the prediction we have to make.
Hope that helped a lot. Let me know any further questions.
:)