Here are just my initial thoughts....as we plan to visit india in march from chicago, we were considering making a 5-7 days stopover in London. I know it is beginning of spring and the weather could be chilly. Any thoughts if this would be a good time or I rather hold off for summer?

You really can't tell. It could be sunny and dry in March, it could be raining in summer.
In March usually flowers and trees start coming out, days are getting longer, it could be nice. Then again, it could snow.

Plenty of things to do indoors in London if the weather is not good.

My birthday is in early March and I live in London. Some days we eat birthday lunch outside at the pub, others it is cooler and might have a light shower or two. London is failrly mild but you really can't say what the weather will be. It will likely be a mix of spring sun, spring showers and cloudy periods all in the same day.

This could be true for most days of the year haha!

Rain showers are great for popping into a pub or a museum and a good umbrella and rain jacket cover you in a pinch!

London, in my opinion, is great at any time of year, but especially outside the summer months. Compared to Chicago, it should be downright balmy.

Depends what you're wanting to see, and what the vagaries of the weather might throw at you. To judge by recent years it might be peak time for the early spring flowers, and we might get a foretaste of summer. Or there can sometimes be a late cold snap with a flurry or two of snow.

But if your interests are mainly indoors in museums and shopping and so on, the weather won't make much difference. The daylight hours will be lengthening, but daylight saving won't kick in till the 25th .

>>Any thoughts if this would be a good time or I rather hold off for summer?<<

One doesn't choose London for the weather really. ESPECIALLY since it could be just as nice in March as in July or October . . . or not.

I've been in London in every month of the year and me personally - I'd rather be there in March than in August. Plus it is the luck of the draw - as soon as you book for say June/July -- it will turn out to be the coldest/wettest summer in 30 years . . . or not.