I use a windshirt anorak that way. It works very well.
It keeps from having to, frequently, add or remove insulated clothing or a rainshell substituting for a "windproof" that regulates core temperature better.
The trick is finding the right balance of wind resistance, breatheabity or ventilation, and resist a brief shower or provide for time to get into rain gear or get to shelter; some windproofs have a different fabric for underarms and sideseam panels to avoid sweat if you perspire a great deal.
For real rain, I have rain gear.
I find, as a practical matter, there is more frequent need for regulating core temperature in wind and weather, than for dealing with rain.