Yes weather could be a factor, but given the high population density of Singapore, I would attribute the success to the Govt.

Note that there have been more than 100 cases now with no deaths.

Some of the less known measures that Govt. took

* Encouraging companies to plan Business continuity plans

* Govt. Whatsapp group provides accurate information, preventing spread of fake news

* Govt gave each household masks just to stop the panic

* Free healthcare for all suffering from coronavirus