I often refer to soil temperature and day to germination data when planning when to start vegetable seeds for the new season.
Here are two useful tables. One provides optimum temperatures for germinating vegetable seeds. The other shows the approximate number of days to emergence at various temperatures.
I find these two especially useful for determining what temperature to set my heat mat thermostat. The latter is especially useful for those kinds that are slower to germinate, or when the seeds are old and may not be as vigorous as new seeds.
A heat mat is the number one accessory I would recommend to everybody who wants to start almost anything from seeds. These are all factory set at about 70º. By adding a thermostat you can adjust the temperature up incrementally. As a case in point, cucumber seeds will pop up in 3 days if you set the thermostat for 85-90º. At 70º it will take a week or more.