How to find where summarizing met certain criteria ??

Hello,
I have rows like this one (daily temperatures)

jan feb mar apr may jun jul aug sep oct nov dec
1___3__4___6___9_15__21_20_15__9__5___2

What I need? I have to find where is sum of temperatures for example 300, or 1000. Starting from march for example, now....my question is: Is it possible in excel and how?Which function?

As you can see I am not expert in excel....

Regards

P.S. Of course, I need to multiply jan with 31, feb with 28, etc.