This is quite common, especially if there are big seasonal changes in temperature. When we lived inland and at high altitude (extreme weather patterns), I found that my basal requirements increased by about 30% during winter. Presumably it is because the body needs to burn more fuel to keep warm in winter, and needs more insulin to do this. Reduced activity levels and a slower metabolism in winter also cause insulin sensitivity to weaken, increasing the amount of insulin required.
When we moved to the coast, it stopped happening. I now seem to have the same basal requirement all year round. It could be because weather patterns are more moderate. Change in lifestyle and age could also have something to do with it.
