Is boiling water enough during monsoon, or do you need a filter?

A rolling boil for one minute reliably kills bacteria, viruses and protozoa including the usual monsoon culprits, so for biological contamination boiling is genuinely sufficient. What boiling does not remove is chemical contamination, heavy metals or turbidity — it actually concentrates dissolved solids slightly as water evaporates. So the answer depends on your supply: if the risk is sewage contamination during monsoon, boiling works; if the concern is industrial contamination or hardness, you need filtration. Many households need both, and cooling boiled water in a clean covered vessel matters as much as boiling it.