If you're struggling for ideas on what to do in Kuala Lumpur on a rainy day then you will be glad to know that there are plenty of museums to visit. Maybe visit the National Textile Museum for an insight into how traditional fabrics such as the famed batik and songket are made, or the Islamic Arts Museum for beautiful works of Islam-inspired arts. Or you can just go to the National Museum for a quick tour on the general history of Malaysia.
Your host can serve as your private guide and driver, so you won't have to worry about commuting and facing the hectic traffic alone. You'll get to stay dry the entire day while appreciating the country's unique history.