I was re-reading my Genki text the other day regarding intransitive verbs and ている and it stated that when intransitive verbs take the ている form they exclusively refer to the state resulting from the change, i.e.
窓が開いている。
The window's open.
お湯が沸いている。
The water boiled.
However, with certain phrases such as 雨が降っている can the meaning be both 「It's raining/It has rained」 ? Which interpretation would be more appropriate 「It's raining」 or 「It has rained」? I would interpret it as 「It has rained」.
Is it a set in stone rule that all intransitive verbs take the result of change form rather than the "-ing/progressive form" or is this just loose rule genki introduced with exceptions?
