A client just asked me why I had selected 105°F as the ambient temperature for Sacramento California area when determining derating factors for electrical conductors. I was stumped as to a precise answer. Just last week I noted it was 106°F in the shade for the hotter part of the day for several days in a row, according to the temperature sensor in my car. As my car is probably not an approved scientific method my question is are there specific charts that we could or should be looking at to determine annual temperatures?
When I look at Climate Sacramento - California and Weather averages Sacramento I am not seeing anything like 106°F in fact the average high is 92°F.
Should I be using the average high? As the higher temperature peaks last more than 3-hours (borrowing from long continuous load heat derating) I am not sure I am comfortable with using 92°F.