weather in around 25 march to 10 april

Hi ,
planing to visit japan around 25 of march to 10 of april, what is the weather in those in tokyo and nara/osaka? what cloths should i will bring?
what is cherry blossoming is that time.
is it better to delay and visit from 1 of april to 16 of april is the weather difference are worth for the delay in the visit?

hope that you will help in some of the question.
Thanks , Pascal.

what is the weather in those in tokyo and nara/osaka?

Here you go:
http://www.japan-guide.com/e/e2273.html

what is cherry blossoming is that time.

About the timing of cherry blossoms:
http://www.japan-guide.com/e/e2011_when.html

is it better to delay and visit from 1 of april to 16 of april is the weather difference are worth for the delay in the visit?

Statistically speaking, you raise your chances of having slightly warmer days (by one or two degrees). In praxis, the weather is changing dynamically and it could be warmer in late March than in mid April. I don't think the weather should be a factor.

But the cherry blossoms could, however, right now it is too early to judge when the blossoms will be best this year.