The police are on duty all the time no matter how big the wind is and how hard/heavy the rain is.
坚守 [jiān shǒu]
[释义] stick to; hold fast to; stand fast; hold one's ground;
[例句]因此,一些分析人士越发怀疑,美联储不会坚守在仲夏提高基准利率的计划。
Some analysts therefore are increasingly skeptical that the Fed will stick to its midsummer timetable for raising its benchmark rate.
如果特指某局的警察,应该加上 the,即 The police have been sticking to their post;如果泛指各处的警察,则不需要定冠词,即 Police have been sticking to their post 。