This is the 139th most frequent Portuguese word.
risco
Risk or scratch/mark.
In this sentence, 'risco' means 'risk', indicating the possibility of something (rain in this case) occurring.
O risco de chuva é alto hoje.
The risk of rain is high today.
Here, 'risco' refers to a scratch or a line drawn on a surface.
Ele fez um risco no papel com o lápis.
He made a scratch on the paper with the pencil.
In this example, 'riscos' (plural of 'risco') means dangers or situations involving uncertainty and possible undesirable outcomes.