完整代码如下：

# -*- coding: utf-8 -*-
"""
Created on Fri Jan 12 14:35:14 2018

@author: Administrator
"""

from turtle import *
from random import *

def ground():
    hideturtle()
    speed(100)
    for i in range(400):
        pensize(randint(5,10))
        x=randint(-400,350)
        y=randint(-280,-1)
        r=-y/280
        g=-y/280
        b=-y/280
        pencolor(r,g,b)
        penup()
        goto(x,y)
        pendown()
        forward(randint(40,100))

def snow():
    hideturtle()
    speed(100)
    pensize(2)
    for i in range(100):
        r=random()
        g=random()
        b=random()
        pencolor(r,g,b)
        penup()
        setx(randint(-350,350))
        sety(randint(1,270))
        pendown()
        dens=randint(8,12)
        snowsize=randint(10,14)
        for j in range(dens):
            forward(snowsize)
            backward(snowsize)
            right(360/dens)

def main():
    setup(800, 600, 0, 0)
    tracer(False)
    bgcolor("black")
    snow()
    ground()
    tracer(True)
    mainloop()
main()

效果图如下：