Yiwu city is very hot in the summer, but also very cold in the winter. On the occasions i have visited in january, it has been bitterly cold. Temperatures rarely rise above freezing in the evening. It is mostly sunny though, with little or no wind. In answer to questions about the commodities market. In my experience, the main market is the place to go for new suppliers. Once you have found the suppliers you need, they will generally take you to their workplace to show you their full range. Be prepared in winter as the market has no heating. The market, from my experience would appear to be approximately 150m wide by on 3 or 4 levels (depending on which section you are in. It is several joined buildings stretching approximately 1 - 1.5km long. This would make it between 450,000m2 at the smallest and 900,000m2 at the largest. My estimate is based upon my memory. This could be quite wrong, but it is a good guess. Fortunately each building/section deals with specific commodities so it shouldnt take too long to walk round. If you do not stop at stalls on your first day you will be able to cover all the areas you need to in one day.