Declination is the angle the sun makes with Earth's equatorial plane.
During the Summer in the Northern hemisphere it is positive.
Whilst during the Winter it is negative.
At the Equinoxes, when the Sun passes through the equatorial plane, declination is zero.
In the Summer the declination will be 23.5o above the equatorial plane.
In the Winter it will be 23.5o below the equatorial plane.