I recommend looking at "Checklist" in "Science Fair Project Question" (https://www.sciencebuddies.org/science- ... ctquestion
) by Science Buddies to check if you have a good science fair project question.
I assume that your independent variable is going to be temperature. If you are going to rely on outdoor temperature, make sure that the temperature readings are not the same for all the days you are going to perform the experiment.
I hope this is helpful. Best of luck with your experiment!