Tomorrow (Feb 22, 2011) is a foggy day with low visibility.
If you are going to hike the Great Wall of China around Beijing tomorrow, you are kindly advised to postpone your travel plan to the day after tomorrow (Feb 23, 2011).
If you have no other choices, Mutianyu Great Wall and Juyongguan Great Wall are recommended to avoid the tourist crowds and also for easy walking. Take care and have a nice day!