Temperature and weather can have a huge impact on power prices. Small examples:

* 90 degree day => more air conditioning usage => power goes up

* 70 degree sunny day => that's also July 4th (holiday, not a work day when factories or heavy industry are running) => lots of people go outside + it's a holiday => power consumption goes DOWN

* 10 degree difference colder/hotter => impacts resistance of power lines => impacts transmission congestion credits => impacts power prices

It's a fascinating industry. One power trading company that I consulted for had a meteorologist who was also a trader. They literally hired the dude from a news channel if I remember it correctly.