In reply to mysterion:
Of all of this, the most stupid suggestion is that "will I really be out in bad weather?"
I'm not sure whether you have ever noticed this but there is this phenomonen called a cloud. When a cloud gets really really full which can happen over the course of an hour or two, the cloud bursts and all the inchy wincy water droplets fall back out of the sky. Sometimes they fall as frozen stuff, which is usual called snow or hail. When its warm it will be water and is called rain. It can rain, snow or hail at any height depending on how warm it is. Otherwise called what temperature it is. When the temperature is cold, and it snows, the snow lands on the ground or sometimes on you, and as you are warm and the snow is cold, it melts. This makes the snow into water, which makes you wet. When it's raining, this also makes you wet. Wetness leads to you getting cold - this magic spell is cast on you called convective cooling. This can lead to you being very cold and shaking like a leaf. When you shake enough like a leaf you get really really tired and sit down in the snow and die like a numpty.
Sorry, I know the extreme sarcasm needle just went through the roof, but summer storms in the alps are serious. Very very serious. They can kill you quickly and can arrive at any time and with very little notice, leaving you vastly over extended and in a dire situation. Having been through quite a few alpine storms, including getting hit by lightening when the day had started off with 50 mile visibility, I would suggest you are lining yourself up for a darwin award by not taking at the very least a waterproof jacket. Trousers I can understand, gaiters are useful if you are really confident and will stop snow going down your boots and soaking your feet. You are not in a situation that if you walk in a straight line for an hour or two you'll get to the road like you can pretty much anywhere in England or Wales.
Look at super lightweight trousers - they're compact and need not take up much room in your pack as that's where they will be until you need them. Softshell can work too if you get the right stuff. Gaiters, if you don't want gaiters then either look at shorty gaiters made of softshell fabric just to keep the snow out, or get trousers with inbuilt snow gaiters. Just don't go out with too little stuff - it can kill you. There is a fine line between light is right and too light is dead. Build your experience by taking too much stuff and slowly whittling it down - it won't take that long to learn.