Power windows fail when hot outside

The vehicle is a 1998 GMC Sierra. This problem developed last summer and has started back now that it's warming up. Whenever the temperature is in the high 70s or above outside, the power windows will not go down (I would assume they don't go up either, but they're always up when I've got in and tried). There is no hum like a motor trying to operate or anything. I tried the switches on both the driver and passenger side and none of the switches will cause the windows to go down. After the temperature goes down outside, the windows work fine again. I haven't had any trouble out of them otherwise, so I wouldn't think it would be the switch being dirty. I'm wondering what components would be affected to the point of failure at around 80 degrees outside. I think there was a fusable link put on the power windows a couple of years ago due to a recall (it's questionable whether the dealership actually did the work). It seems like that might be related, but wouldn't a fusable link fail completely if overheated and not start working again when it cools down outside. Any suggestions are appreciated.