There is no doubt that temperature, and humidity, affect the performance of harddrives, or any piece of machinery and living organism as well. Plextor lists the environmental conditions for the 716a on page 118 of my user manual: Operating Temperature 5-40 C and Operating Humidity 20-80% (non-condensing).
My ambient weather conditions could pose a problem since humidity has approached and sometimes exceeded 80%. Thankfully, ambient room temps have been less than 40C, but not by much on occasion due to greenhouse-like effect of the windows in the room. I have a Thermaltake Hardcano 13 with 4 temperature probes. The highest temp that I have seen so far has been 37.3 C located on the heatsink of the GeForce 6800 Ultra, a major blowtorch of a heat producer. Currently, the Nvidia Control Panel Display states ambient 40 C and GPU Core Temperature 55-56 C. The Hardcano 13 reports 36 C at the video card's heat sink. The four 120cm fans in my case (front over the harddrives, side over the video card, back and top blowhole) really help to keep things cooler in the Lian Li 7B-Plus modified case.
Below are two PxScans of Verbatim 16X DVD+R media, where the discs came off the same spindle with 2 other discs used between them, so they are not quite consecutive. The data and its amount are different as were the date and environmental conditions at burn time, being slightly warmer and significantly more humid at the time of the second burn and scan. Also, the data burned on the first scan came from multiple partitions on the drive while the second graph's data all came from the same partition. Also, two other discs had been burned prior to the first scan while this was the first burn done that day in the secong scan. The computer was on for roughly the same duration prior to the burn and scans.
Why I tell you all this is to point out that conditions favored better burns for the second graph except for temperature and humidity, yet, the second graph shows a slightly less favorable burn.
So... an extremely small sampling (of 1!), more anecdotal than empirical, and one in which more than a couple of varying parameters are involved prohibit the validity of my conclusion. That stated, it would appear that temperature and humidity do play a part in the quality of the burn: PIE avg of 0.28 vs. 0.38 and PIF avg of 0.0044 vs. 0.0050 for the first and second graphs respectfully.
Bottom line: Keep room as cool and humidity-free as possible, add fans (larger the better for improved quiet), pay attention to airflow inside the case with thoughtful cable/wire placement, consider a drive bay cooler, and burn at slower speeds and at times of day when the ambient room temperature is cooler. Best media for your burner is always a good idea for improved error rates too (Taiyo Yuden TY02 best for me so far.)
WOW! I tried to attach the first scan but the forum's application won't do it since I uploaded it to a different thread previously, and that's despite renaming the file too! You can find the first scan in Post your Plextor DVD quality scans here currently on page 51. It is the second PxScan (third png overall) with the comment "Verbatim 16X Burned At 8X".