"It will be" vs "It is"

[civetcat]

1 It is necessary to bring an umbrella when ...
2 It will be necessary to bring an umbrella when ...

From my interpretation, #1 is a definite requirement. The speaker is probably some authoritative person i.e. experienced or has some knowledge of the situation to offer that advice.

In #2, the speaker is trying to be tactful when imparting the advice. Rather than forcing the issue; the speaker leaves it up to the recipient to decide whether or not to bring an umbrella.

Your comments on my comments ?

Thanks

Civet Cat
H5N1 virus carrier

[Tdol]

2 could have various uses, including the one you suggest. It could be used for emphasis or to denote a change in circumstance.