Glasgow weather is fairly normal by Scottish standards. Basically that means that it can downpour with rain at any time. So its always wise to be prepared.
Summers can be warm and balmy and tend to begin around the beginning of June. However there is always the threat of rain and its safe to bet that you will see a little shower at least on your travels. The winter period is cold but doesn’t start until around the end of October.
The best time to come is obviously in the summer when there is generally less chances of rain. However the Scots are hardy folk and the rain never really deters them from doing what they want.
As long as you wrap up warm you should enjoy your stay in this vibrant and happening city.