As evening approached on 18 June 2017, Sunday, a late developer of Sumatra squall made its presence felt in Singapore.
Strong winds blowing from southwest brought heavy rain coupled with thunder and lightning, which lasted over an hour.
“Squall-lines usually occur during pre-dawn and early morning, and are most frequent between the months of April and November. However, squall-lines can occasionally form in the afternoons and move landwards along with the prevailing winds.”
(From Stormy shores: the Sumatras)