The post-Christmas surge of Covid-19 cases in Portugal is empirically estimated using a nonlinear exponential growth equation. The `soft’ lockdown, implemented on 15th January is shown to induce an initial inflexion point from which cases decline, and the subsequent `hard’ lockdown from the 22nd January reinforces this downwards trend. Taking no action would have led to an estimated 20 000 cases per day in the week ending the 15th February. The effect of the soft lockdown, strengthened by school closures and a harder lockdown, avoided this scenario, and curtailed the number of daily new cases to less than 3000 by week ending the 15th February. It is estimated that without the adoption of school closures and harder lockdown measures, the estimated cases in Portugal would be approximately 9700 per day.