A time series of any variable has got a mean and a standard deviation. In general when the value of a variable is within the 1 standard deviation of either sides of its mean value, we can say that of the variable is within the normal range or simply "normal". When the value of the variable is 1 standard deviation above (below) its value, we say the value is "above (below) normal". In case of monsoon season (June to September) rainfall over India as a whole, the mean value (generally mentioned as long term average) is 89 cm and standard deviation is 9cm (about 10% of mean value). Therefore, when the rainfall is within 10% of its long term average, the rainfall is said to be "normal" and when the rainfall is 10% more (less) than its long term average, the rainfall is said to be "above (below) normal".