Charles H. Spurgeon 1834-1892
This  preacher needs no introduction.  Read an article he wrote on the subject of Street Preaching entitled
"OPEN-AIR PREACHING
A SKETCH OF ITS HISTORY AND REMARKS THEREON"

An Excerpt from the article: I once preached a sermon in the open air in haying time during a violent storm of rain. The text was, "He shall come down like rain upon the mown grass: as showers that water the earth," and surely we had the blessing as well as the inconvenience. I was sufficiently wet, and my congregation must have been drenched, but they stood it out, and I never heard that anybody was the worse in health, though, I thank God, I have heard of souls brought to Jesus under that discourse. Once in a while, and under strong excitement, such things do no one any harm, but we are not to expect miracles, nor wantonly venture upon a course of procedure which might kill the sickly and lay the foundations of disease in the strong.

Quotes:
"If I were utterly selfish and had no care for anything but my own happiness, I would choose, If I might under God, to be a soul winner, for never did I know perfect overflowing, unuterable happiness of the purest and most ennobling order till I first heard of one who had sought and found the Saviour through my means."

"It would be very easy to prove that revivals of religion have usually been accompanied, if not caused, by a considerable amount of preaching out of doors, or in unusual places."