Who spoke?

The sun was warm but the wind was chill.
You know how it is with an April day.
When the sun is out and the wind is still,
You're one month on in the middle of May.
But if you so much as dare to speak,
a cloud come over the sunlit arch,
And wind comes off a frozen peak,
And you're two months back in the middle of March.
-  Robert Frost 


So true! Who spoke??