It is rained because rain is a regular verb. This means the past tense is formed by adding -ed.
The past tense of "rain" would be "rained".It rained is the past tense
The past tense of "rain" is "rained," and the present tense is "rain."
The past tense is rained. The future tense is will rain.
The past tense for the verb "rain" is "rained".
Will rain is the future tense of rain. Rained is the past tense.
The simple past tense of be is was and were.The simple past tense of rain is rained.
The past tense verb for "it rained last night" is "rained."
It rained.
rained
rained
Yesterday it rained.
That is the correct spelling of "raining" (having rain). The sound-alike word is "reigning" meaning serving as king, queen, or royal sovereign, or (metaphorically) being in control or authority.