From a distance with the available information, that is difficult. To help, one would need: year of construction, wall structure, close-up photos of the spot from inside and outside, and whether there is really a draft there or if it just feels that way due to the temperature difference. Generally, I become alert with rainwater downpipes and an unusually cold and possibly damp corner – but it does not necessarily have to be due to the downpipe. If it is clogged and water penetrates the wall somewhere, that part will also become cold. Without more information, nothing more can be said.