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

winter solstice

summer solstice

vernal equinox

autumnal equinox

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

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.