Do not say: “It is too hot today”*, if you mean (se quer dizer):
                  It is very (muito) hot

*In sentences like this, “too” does not mean very …
 it means: excessively (excessivamente)
(The Collins Concise Dictionary says it means: “to an excessive degree”)

In English, you say:

“It’s very (muito) hot today – I want to go swimming.”
or:
“It’s too (excessivamente) hot for tennis – I want to go swimming.”

Of course (claro), “too” has another meaning (um outro significado) … it means: also (também)

For example:
“Wait for me – I want to go swimming, too.”