I know it's probably not what you want to hear and I may catch some flack too - but in warm weather a M686 is not really conducive to daily carry! I own a M586 (same gun but in blue) and other than using it at the Range or in the Woods, I don't carry it. There are smaller and lighter models (M13, M65, M66, M19) that are way more conducive for warm weather carry and they will shoot the same cartridges. If you are hell bent about carrying a 357 Magnum in warm weather, get yourself a vintage 3" 65/13 Revolver. Even the 2.5" M66/19 would fit the bill however I prefer the 3" bbl and like fixed sights on a magnum carry gun.
Remember..... if your dress is "out of place" for the weather and location, you will be found out quickly! No one wants to wear a windbreaker, vest, over garment in 90º + weather and those who do are out of place and people in the know understand why! Bottom line here is to get a smaller and lighter hand gun IMO. Then practice with it until you can consistently shoot it accurate and efficiently. I apologize if that is not what you want to hear - they're just my honest thoughts.