In general, Fez and Meknès are safe cities. In Fez—less in Meknès—pickpocketing and unwanted hassle from hustlers and faux guides will be the biggest concern. Harassment from those offering to be tour guides or drivers is best avoided by smiling and firmly saying "no thank you," preferably in French or Arabic. Try not to become visibly agitated, as it could exacerbate the situation.
You can safely explore Fez medina during the day, but ask at your hotel if there are any areas you should avoid after dark. If you get off track, turn around and head back to a more populated area. If you are followed, enter a store, hotel, restaurant, or café and ask for help. At night, poorly lit medina alleyways can be intimidating but are not necessarily unsafe. Often hotels and restaurants will dispatch someone to escort you to your destination.
From December through January, heavy snowfall may cover Middle Atlas roads; however, the snow-removal systems in places such as the Azrou Cedar Forest are relatively good, with cleared driving routes. More remote roads (marked in white on the Michelin map of Morocco) will be difficult to access or completely closed in snowy conditions. Driving off-road or to natural sites such as the Cascades d’Ouzoud in winter, when snowfall can be significant, is not advised.