Authentic Supplication Number 182.

The Prophet  was such that if he would see a collection of clouds starting to form in the horizon he would leave work, even if he was in the middle of supplication, then he would say: Allahumma 'innee 'a`outhu bika min sharriha (196), then if it would rain, he would say: 'Allahumma sayyiban hanee'an (197).

Footnotes.
(196) O my 'ilah I solicit Your protection from its evil.
(197) O my 'ilah make it go straight to the target, and make it a means for our well-being.

Reporters.
Reported by Abu Dawood, An-Nisa'ee, and Ibn Majah. Al-Albani said that it was further reported by Abu `Uwanah in his Saheeh with sound ascription according to Muslim's conditions. Al-Albani included this hadeeth in The Authentic of Good Sayings as #128.