Use of recent volatility level
The volatility of historical exchange rate movements over a recent period can be used to forecast the future.
Use of historical pattern of volatilities
If there is a pattern to the changes in exchange rate volatility over time, a series of time periods may be used to forecast volatility in the next period. For example, the standard deviation of monthly exchange rate movements in the Canadian dollar can be determined for the last several years. The volatility forecast may be based on a weighting scheme such as 60% times the standard deviation in the last year, plus 30% times the standard deviation in the year before that, plus 10% times the standard deviation in the year before that