The North Pole is tilted closest to the sun during the:

winter solstice

summer solstice

vernal equinox

autumnal equinox

i think its closest to the summer solstice

Explanation:

23.5 degrees

Near June 21 the north pole is tilted 23.5 degrees toward our Sun and the northern hemisphere experiences summer solstice, the longest day of the northern hemisphere year.

It is tilted closest to the summer solstice and farthest in the winter solstice.