  The weather at Xinglong Observing Station, where the Guo Shou Jing Telescope
(GSJT) is located, is strongly affected by the monsoon climate in north-east
China. The LAMOST survey strategy is constrained by these weather patterns. In
this paper, we present a statistics on observing hours from 2004 to 2007, and
the sky brightness, seeing, and sky transparency from 1995 to 2011 at the site.
We investigate effects of the site conditions on the survey plan. Operable
hours each month shows strong correlation with season: on average there are 8
operable hours per night available in December, but only 1-2 hours in July and
August. The seeing and the sky transparency also vary with seasons. Although
the seeing is worse in windy winters, and the atmospheric extinction is worse
in the spring and summer, the site is adequate for the proposed scientific
program of LAMOST survey. With a Monte Carlo simulation using historical data
on the site condition, we find that the available observation hours constrain
the survey footprint from 22h to 16h in right ascension; the sky brightness
allows LAMOST to obtain the limit magnitude of V = 19.5mag with S/N = 10.
