Like a dry robe but not as warm

[imabitjealousandembarassed]

I've got a regatta copy dry robe and it's a brilliant raincoat but in the mild weather for my walk to work it's way too hot. Anyone got any recommendations for a similar shape raincoat (oversized triangle type) that is as rainproof (I walk even in heavy rain) but not as warm?
I cant spend hundreds on a RAINS one

Have a look at M&S, they have a few. There was a thread about it recently