Earth Hour

Hi everyone now i am going to talk about earth hour.Actually the advantages of the earth hour was to save the earth to prevent for globle warming.When its is earth hour we must not use eletricity the whole day.The day is 28.3.09(ACCORDING FROM MY TEACHER).The disadvantage is when its is a freezy cold day we must use the eletric heaters to bath ,what happen it is freezy cold day on 28.3.09?