Plenty of information on the subject can be found in different places. I don’t remember them all, only the following :
http://www.omafra.gov.on.ca/english/crops/facts/info_tomtemp.htm
The Effect of Extreme Temperatures on the Tomato and Pepper Crop
I germinate at 78F to 80F ( 20 ŕ 35) C)with the domes on.
Once the seedlings are up 2" high I remove the domes so air can start circulating. This is a critical stage where damping off can be a big problem. I leave them on the 78F (25.5° C) blanket for about 3 more days until they get their true leaves, and then move them to a 60F ( 15.5 °C) blanket for a week until I'm ready to transplant from multi-cell trays to pots. At this point they are hardy enough to withstand 40F (4.5° C) lows.
For tomatoes, germination peaks at 86F (30°C), but is still pretty high from about 68F ( 20°C) to 95F (35°C), and is lower at 41-68F (5°C – 20°C)..
http://www.heirloomseeds.com/germination.html
seed germination soil temperatures
Pepper 25.5 to 29.5 C 78-85F 0 to 14 days
Tomato 24 to 25.5 C 75-78F 7 to 14 days
Tomodori, a French site :
Tomato
Minimum temp : 10C / 12F
optimum range :
16C - 29C / 61 – 84F
optimum temp : 29C 84F
maximum temp : 35C 95F
http://www.tomatoville.com/showthread.php?t=25599&page=5 post 74 etc etc. very rich
Using a thermostat, at least a thermometer, is recommended unless you are ready to roast your seeds sooner or later…