To find the current temperature, you can subtract the change in temperature from the temperature yesterday.
Yesterday's temperature: 13°C
Change in temperature: -18.6°
Current temperature = Yesterday's temperature + Change in temperature
Current temperature = 13°C + (-18.6°)
Current temperature = 13°C - 18.6°
Current temperature = -5.6°C
So, the temperature now is -5.6°C.