So here's a more subjective report. The most consistent aspect of Powell's weather is the potential for quick change. More often than not winds are calm, but they can be fierce when strong weather fronts move through the region. Temperatures can plunge dramatically and strong winds can produce dangerous wind chills in the winter. Even in the summer, it's a good idea to carry a light coat.
Evenings are frequently cool, but it can be very hot.
It seems like every August we get a hot spell where the temperature climbs over a hundred every day for a week or more. Powell is high. Occasionally a storm will drop a lot of snow or rain, but that's the exception rather than the rule. When the winds are calm and the skies are clear, even the cold temperatures of winter aren't all that bad. Most of the time the skies are not cloudy all day.