With made-to-measure and bespoke tailors crafting everything from pajama sets to safari jackets for the modern man, it would follow that raincoats should feature in their repertoire. But custom-made rainwear remains a rarity, a seeming oversight considering the difficulty of altering traditional raincoats.

Unlike woolen overcoats, whose sleeve lengths can be easily adjusted, coats made from water-repellent cotton or cotton-blend fabrics tend to “scar” with alteration. As Robert Squillaro, the senior vice president and chief merchandising officer of J. Press warns, attempting to alter the retailer’s 100 percent cotton Grenfell raincoat is a dangerous business.

“Tightly woven cotton fabrics that have been tailored and pressed into garments cannot have the seams let out or the sleeves lengthened because you will see the stitch marks or creases that were either sewn or pressed in,” he tells Robb Report.

Aside from the nature of the fabric, Squillaro points out that a raincoat’s sleeve cuffs typically end with a fusible that creates a crease. Trying to undo this crease without leaving the original mark behind is an impossible task.

Men whose proportions fall outside of traditional sizing might seek out a bespoke tailor to stay dry. But as Paolo Martorano of the eponymously named bespoke tailoring business explains, popular rainproof fabrics like Loro Piana Storm System don’t play nice with a benchmade tailor’s tools.

“Storm System is an exceptional product. The issue with the membrane is that it is a very dense synthetic, which, in pressing, can melt and cause damage to the tailor-shop irons,” he says. “Most high-end factories or made-to-measure workshops which work with this fabric are equipped to deal with it in ways that bespoke tailors simply are not; this includes special sleeves to cover their irons so they can work with this cloth properly without fear that they’ll damage their equipment.”

Cad & The Dandy has addressed this issue by partnering directly with Mackintosh to provide rainproof outerwear in a made-to-order capacity. Through its ongoing partnership with the maker—whose founder Charles Macintosh introduced the first rubberized cotton raincoat in 1824—clients can be fitted for a custom Mackintosh at Cad & The Dandy’s London or New York showrooms.

“A Mackintosh is 100 percent waterproof. In order to achieve this, every seam is bonded. Tailors often don’t have the means to adjust a bonded seam or reseal,” Cad & The Dandy’s US managing director Steve Knorsch says of the partnership’s necessity.

After a client selects a rubberized cotton and chooses between either the classic Oxford raincoat or the hooded Granish model, their measurements will be applied to an existing size block and manufactured into a finished garment at Mackintosh’s UK factory in eight weeks.

Angel Ramos, the founder of the eponymous New York-based custom clothier, ties the scarcity of custom raincoats to a lack of imagination.

“Custom rainwear isn’t difficult to find, per se, but really it’s more that people don’t think about rainwear when they think about custom,” he says. “For outerwear, we tend to think of all types of classic tailored overcoats, but because rainwear falls into this sort of ‘technical’ function territory, people don’t think it’s available custom.”

Ramos’s solution was to design a raincoat that matched sartorial gravitas to practical performance. His water-repellant twill trench coat, available both made-to-order and made-to-measure, mimics a polo coat with such classical features as an Ulster collar, half-belted back and gauntlet cuffs. But it is made from a cotton-wool Dormeuil fabric whose high-density weave and nanotechnology treatment easily resists rain droplets.

However, all that weather resistance comes with a price. “The density in this fabric means mending is very tricky, since it is physically difficult to push a needle through the fabric to make any corrections that might be necessary,” Ramos says of the miraculous but tough-to-tailor textile.

Creating custom rainwear is not without its challenges, but the good news is that makers are stepping up to serve those who require it. As for those who can fit into an off-the-peg make, “You could do worse than a classic Burberry,” Martorano says.