Summer rain jacket recommendations I'm commuting an hour each way each day in summer now and it rains sometimes.

I have a GoreTex jacket which I bought 10 years ago for walking in. With additional inner warm clothes I wear it in temperatures down to -5C (23F). I can wear it with a shirt when cycling when the temperature is up to (i.e. below) about 15C (60F): it keeps me fairly dry; and if it doesn't (in a downpour for up to an hour) then at least it's wind-proof i.e. fairly air-tight i.e. insulating on a bike and can therefore keep me warm after I'm soaked and it's still raining.

It's too warm to wear in summer though, when biking. In a light rain with a temperature over 22C (70F), if I wore it zipped up I'd get soaked with sweat: and might as well, instead, arrive at work soaked with rain.

What can you recommend for a summer rain jacket? I'm guessing that options include:


'Breathable' (e.g. GoreTex) bike-specific jacket
'Waterproof', vented material
'Poncho' of some kind
'Nothing': instead, insulating clothes to regulate temperature even when wet (I have a pannier), and change of (dry) clothes at the destination.


I'm looking for something that will:


Last for an hour, commuting 18 km
Rainfall of 1 mm to (if I'm lucky) 5 mm per hour
Temperatures of 22C and above


I went to a bike store. One option there was a lightweight waterproof, with venting (e.g. in the armpits) for a bit over $100. Another option was a "GoreTex PacLite" for about $250, which doesn't have venting ("unlike cheaper, waterproof, doesn't need venting").

My uncle flippantly recommended a poncho; however the few people I've seen wearing one on the street seem to be riding at only about 10 kph, which would more than double my journey time: is that right, or can they be faster?

I was tempted to buy the GoreTex but it's expensive enough that I wouldn't want to regret the purchase, so I hoped to ask you. Can an unvented jacket be usable when zipped up and biking in warmer temperatures, if it's (for example) GoreTex? Are there good reasons for or against vents?

I have a pannier to carry it in when it's not raining (I use the pannier only for whatever spare clothing I may want to carry that day, and the U-lock); so light-weight would be quite nice but pack-ability seems less important.
In my personal experience, anything you wear while riding that is even moderately water proof will trap heat and sweat and for me, I will end up just as wet if I had ridden with or without the jacket.

GoreTex and the like are just riding an edge of being helpful.  Short rides, cool temps, perfect.  Long rides, doesn't matter, you are going to get wet.  From the inside or the outside.  :)