What you’re going to read is perhaps the most valuable gardening instruction that has ever been offered to you.
When to sow
On each pack of seeds you buy is on the back 4 or 5 colorful areas and planting dates for each area. Or you find enigmatic hints of the type “whenever the soil can be worked”, “after it is sufficiently moist”. Plant when the soil has the right temperature! These indications have virtually no meaning. On the other hand, the temperature of the soil will never mislead you, because the temperature of the soil changes slowly: it warms slowly at the beginning of the hot season and cools slowly in the cold season.