Singular spectrum analysis (SSA) is a popular tool for analysing and forecasting time series. The SSA forecasting algorithms have two parameters which should be chosen by the researcher or using the so-called automatic choice based on the root mean squared errors (RMSE) of retrospective forecasts. We study the sensitivity of the RMSE and investigate the reliability of the automatic choice of parameters for forecasting monthly temperature and humidity recorded at three meteorological stations in Oman.