The present tense of rain is:
Rain is present tense. The past tense is rained.
Present perfectI have windedI have woundyou have windedyou have woundhe/she/it has windedhe/she/it has woundwe have windedwe have woundyou have windedyou have woundthey have windedthey have wound
rain would need a suffix if it was to be a verb. Rain is a noun by itself.
Water is the future tense of water. 'I am going to water the plants'. Watered in the past tense. Watering is the present tense.
The past tense is rained. The future tense is will rain.
The verb is is the present tense.
Will rain is the future tense of rain. Rained is the past tense.
The past tense of did is did. The present tense of did is do. The future tense of did is will do.
It was, (past tense) it is, (present tense) it will be( future tense)
Past tense I had Present tense I have Future Tense I will have
"Has" is in present tense. The past tense is "had".
No 'is' is present tense. am/is/are = present tense was/were = past tense