int precip;
for (int i = 0; i < 20; i++)
{
   precip = snow;
   /* argument is in days */
   Delay(3);
   /* This sux */
   precip = rain;
}
ok, so let the geek show begin... revised it a bit so it compiles and runs giving some output with a 30 days in between rains. 
#include <stdio.h>
#include <unistd.h>
void Delay(int d)
{
  sleep(d * 24 * 60 * 60);
}
int main(void)
{
  int i, precip, snow, rain;
  for( i = 0; i < 20; i++ )
  {
    printf("snow good\n");
    /* argument is in days */
    Delay(30);
    /* This sux */
    printf("rain sux\n");
  } 
  return(0);
}
woohooo... even freaks can be geeks...