I usually hatch early in the year and we heat with just wood so the temp fluctuates a lot. In the morning the house is cool in the evening its hot and during the night it gets cold so I adjust the temp accordingly. Before I leave for work I turn the bator up by 2 lines almost a quarter turn because I know the house will be cold, when I get home from work I turn it down the same amount because I know the house will be warm in the evening hours before bed I turn it back up again so even though the air in the house varies by sometimes 30 degrees the temp in the incubator keeps amazingly accuate........ I did 2 hatches this way in March and April first hatch was 33 out of 34 and the second was 34 out of 34 fertile eggs hatched.