I took some exposures at 1 sec intervals today, capturing the departure of a large ship. In the beginning the interval was running just fine, but after a while a frame every now and then was dropped, increasingly throughout the session. I was shooting at 1/60 on my old 40D with an Aputure TR3C timer. Outside it was around 0 °C.

Then I went back in to the warmth again and started testing the intervalometer. Inside, I was then able to get it running stable at 1 sec interval even at an exposure of 0,8 sec. I saw the post about hacking the cable, but it appears that the camera can deal with only 0,2 sec dark time while warm - which leads me to think that the intervalometer is not bad.

So it seem that cold weather slows down the camera in this respect. Anyone else that have experienced this?

Don't know, batteries might be weaker when it's cold, but normally I wouldn't see a direct effect on the possible intervals. But one second is already quite short and might bring the camera to the limit after a couple of shots, I'd definitely recommend the intervalometer hack, especially for very short intervals.