I think it's a great idea to change navigation. In the winter, people are less likely to be looking for golfing products, and more for skiing products. Your navigation needs to meet two goals:
- Consistency: the navigation needs to be the same across the site, intuitive.
- Relevancy: the user needs to be presented with the options they are looking for.
Now, it's difficult to achieve both because shopping patterns are not stationary over time. You don't want to change the navigational layout too often, as it may confuse regular users. But it's a worthwhile trade-off in order to provide more relevant options to the user.
I would base any decision to change the navigation on historic data, or else do a test to see which is more useful. In absence of your own data, you can look to something like Google Trends.
Data will reveal patterns over time. In the above graphs, you can clearly see that 'interest' in golf doubles from January to July. Interest in skiing goes up by a factor of 5 between July and January. What this kind of analysis tells you is that skiing is almost irrelevant for most of the year. But, in a very narrow span of 4 months, interest grows substantially. This is when you'd consider changing your navigation to add 'Ski'.