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I have no idea what the weather will be like tomorrow.
Literal
Tomorrow [possessive-の] weather [subject-が] how-become [nominalizer-のか] estimate [also-も] not-attach.
Built around the idiom 見当もつかない ('not even able to form an estimate/guess' → 'have no idea'). 見当 is the noun 'estimate/guess,' つく is 'to attach/form,' and the emphatic も ('not even') intensifies the negation. The embedded question どうなるのか uses the explanatory nominalizer のか to turn the question into a noun phrase that 見当 can take.