Consequently, a Summer invasion would of worked for the RN, less storms, less fatigue on our vessels.
The seas may have been less strong, but only marginally so (remember its the South Atlantic, 50ª S latitude down there) in Summer. BUT, daylight hours would have been considerably longer (almost twice the daylenght) rendering it almost impossible for the RN to close in at night for naval gun fire and leaving undetected before dawn again.
Remember argie A-4s and Dagger´s at the time are daylight/nice weather only fighters. They would have benefitted much more from a Summer war than the RN, being able to operate almost 18 hours a day over the islands, while in a Fall/Winter war they had only 10 to 12 hours a day. Of course that opens up the question: how long could the argie AF keep that rythm of operations before deing of an attrition death?
Also "gulash kannone" issues for the ground troops would have been way less strong in Summer, allowing for better troop feeding and better troop alertness (only a handfull officers had working NVGs, while most of the outposts were basically blind at night).