Planning on traveling very light. Will jeans, khaki's, a couple t-shirts, skirt, tall boots and Nike's be enough for 3 weeks? I will be using public transportation, don't want to have too much to take on a train. My husband assumes it's going to be in the 70's and he can wear shorts the entire trip. Any advise would be greatly appreciated.
Temperatures in September can be unpredictable depending on when autumn properly begins. I would certainly not count on being able to wear T-shirts with no coat, or shorts. I would strongly recommend checking weather forecasts the day before you leave and packing in the light of them.
what are the tall boots for? Going out in the evenings? But you won't be doing that if your husband is in shorts.
I wear shorts a lot myself in the summer, and during the day when I am sightseeing in summer, but I wouldn't count on only shorts for the whole of September.
I was in Belgium/Netherlands this past September, and I highly recommend taking a light jacket/hoodie with you. The weather is much like the United Kingdom and it rained frequently. The most beautiful days I had were in the upper 60s and super pleasant-but I did start out with a zippered hoodie in the morning, which I tied around my waist after lunch. There were also a few days it never made it to 60 and it rained the entire day.
Count on lots of rain, and be pleasantly surprised on days there are none.
I'll echo Philip's advice to check the weather before you leave. I'll start checking the weather at my destination every day about two weeks before I leave. You can look at average temperatures, rainfall, etc. but that won't tell you anything about what the weather will be like once you get to September. I was in northern Germany in July 2010 during a heat wave when it was in the upper 90s every day. The average is in the 70s. A month ago my friend in Hamburg reported daytime temperatures in the upper 60s.