Which preposition to use with forewarnings

of Occurrences 10%

The face of nature seemed to be a mirror of our fortunes, for when I woke the freshness had gone out of the air, and in the overcast sky there was a forewarning of storm.

to Occurrences 1%

The discipline observed on this march was a terrible forewarning to the people of the Netherlands of the influence of the general and the obedience of the troops.

Which preposition to use with  forewarnings