English Basic Explanation - Chapter 65
Ibn Ezra (commenting to verse 4) explains this Psalm as a prayer for rain to be recited during times of drought. This is clearly indicated in the final section of this chapter (verses 10-14) which poetically describes the rainfall the Psalmist begs the Almighty to provide, and the abundance of quality produce that the rains will yield. Indeed, it is customary in some communities to recite this Psalm in Israel during periods of drought, Heaven forbid.
It appears from a number of references in this chapter that it was intended to be recited specifically in the Bet Ha'mikdash. Verse 2 describes to the Almighty as "God in Zion" and speaks of fulfilling one's vows, which often refers specifically to vows involving sacrifices (as in Devarim 23:22 and Tehillim 116:18). And in verse 5, David speaks of the good fortune of those who are privileged to dwell in the Almighty's "courtyards" and "home," clearly referring to the Temple. Indeed, in King Shelomo's famous prayer during the inauguration of the Bet Ha'mikdash (Melachim I 8:35-36) he mentions that when drought strikes, Am Yisrael shall pray in the Mikdash and God will then bless them with rain. Accordingly, David composed this prayer with the intent that it be recited specifically in the Bet Ha'mikdash.
This prayer speaks of God's power to "humble" the oceans (verse 8), which the Radak explains as a reference to the splitting of the Sea of Reeds after the Exodus. During times of drought we ask that just as the Almighty transformed the raging sea into dry land, so is He capable of bringing water to the parched earth.
This prayer also includes a confession on the part of the people that they have sinned, and a request for atonement (verse 4). In many contexts the Torah warns that disobeying God's commands will result in drought and famine, and it is therefore natural for the people to confess their sins and repent in response to drought conditions. God will then, in turn, forgive the people and grant them abundant rainfall and economic prosperity, as King Shelomo prayed: "And you shall hear in the heavens and forgive the sin of Your servants and Your nation Israel, for You shall show them the proper path to follow, and You shall give rain upon Your land which You have given to Your nation as an allotment" (Melachim I 8:36).