Also, unlike most other solar measurements, sunrise occurs when the Sun's upper limb, rather than its center, appears to cross the horizon. The apparent radius of the Sun at the horizon is 16 arc minutes.
These two angles combine to define sunrise to occur when the Sun's center is 50 arc minutes below the horizon, or 90.83° from the zenith.
It was -3°C in the morning and all the ground was frozen, as I got near Loimaa all the fields were frozen over. Luckily roads had been dry before the night and the roads weren't icy. When I got to Loimaa, I went straight to tire shop where my winter tires are held and reserved a time for changing summer tires to winter tires.