Answer: The wind will blow hard.
Usually, to convert something to future tense, we need need to add the word "will" and make minor changes in the right place.
For example, let's say we have the sentence:
I went to the park.
To convert that into future tense, you would say:
I will go to the park.
Lets take your problem:
The wind is blowing hard.
In future tense:
The wind will blow hard.