This topic isn't an unusual one for both LE and private persons lawfully carrying handguns. Even cops who wear duty jackets or longer car coats need to adjust their skills to any variances in their seasonal clothing. Sure, it can be a bit easier for uniform use, as some car coats may have had side cuts so they could be opened and fastened around the gun belt holsters, but inclement weather and having a rain-soaked weapon and holster can still be a concern. The standard 'Tuffy' jackets can simply be lifted up and over the holstered weapon to give some clearance.
I remember attending an outside training week created for plainclothes and 'street enforcement' folks who wore low profile clothing, and one of the requirements of the class was that cops attending had to bring and wear realistic plainclothes or discreet clothing appropriate to their assignments, and which specifically concealed their belt weapons. Students were told that no camera or fishing vests would be allowed.
It was being held in the end of winter, so the temps were cold when using the various outdoor ranges at the hosting agency. One of the topics was to acquaint students with how to draw from under different types and layers of concealment garments, and require they demonstrate the ability in various range sessions throughout the week.
Now, while my plainclothes assignment allowed me to wear a lightweight suit or sport coat, I decided to dress more appropriate for weather conditions that week, and even used different layers. Why not? I often did that when working my other assignment as an instructor on our own outdoor ranges. A sweat shirt, under a zippered fleece and/or a long ski parka. If I could qualify drawing from under those types of concealment garments, I didn't expect my usual sport/suit coat, and the occasional dress rain coat, I wore in my normal duties to be problematic. Train hard, to learn to hope to fight easy, right?
Bottom line, when the basic drill assessment of drawing from under concealment garments and engaging a threat target was done at the beginning of the class, I was able to do the timed drill in less than 1.5 seconds on the first try, which was the recommended goal of the class. By the end of the week I managed to take almost half a second off that time, even wearing the layers.
I still think of the lessons taught in that class when I wear my various retirement clothing, no matter whether I'm wearing a belt-scabbarded weapon or one pocket-holstered ... and that class was a little more than 20 years ago. Of course, it helped that when I'd returned to my own agency I continued to practice drawing and presentation wearing various clothing that was appropriate for seasonal conditions, and I'd thanked the then-head instructor for making us practice that sort of thing as members of the firearms training unit. (Ditto being able to clear stoppages while moving, and even going prone to roll under concealment or cover, but that was another story of lessons applied during that week's training.
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