 A model with time-varying speed of mean reversion, seasonal mean,  local volatility that depends on the average temperature and time for the contract period is proposed.
<clarity>  A model with time-varying speed of mean reversion, seasonal mean,  local volatility that depends on the average temperature and time for the contract period is proposed.
 A model with time-varying speed of mean reversion, seasonal mean, and local volatility that depends on the average temperature and time for the contract period is proposed.