Continentality/Oceanity
The borders are fluent between continentality and maritimity. However, there are several indices, aiming to clarify this question. For instance, the probably earliest one is from Gorczynski (1920):
$$K_{Gorczynski} = 1.6 \cdot \frac{A}{\sin \varphi} - 14$$
where $A$ is the annual temperature amplitude of the location and $\varphi$ the latitude of the location. Another one, which is more often used, is from Iwanow (1956):
$$K_{Iwanow} = 260 \cdot \frac{\Delta T}{\varphi}$$
where $\varphi$ is the latitude again and
$$\Delta T=T_\mathrm{max} - T_\mathrm{min}$$
where $T_\mathrm{max}$ is the temperature maximum and $T_\mathrm{min}$ the temperature minimum. The results are characterized as following:


K &lt; 100: maritime
100 &lt; K &lt; 200: continental
K > 200: strongly continental


To answer the second part of the question: as the indices show, the latitude needs to be considered. Currently I do not have the original publication by Gorczynski or Iwanow here, however there are some papers comparing different indices (there are several more), for example this one. Furthermore, the indices can be looked up in the most climatology basic literature and encyclopedia. At least, it is needed to mention that Gordon Stanger hits the point in his answer in the last sentence: The continentality is just one variable - there are several more. Look for climate classifications, like those from Köppen &amp; Geiger or Schultz.

Edit: Original reference

Gorczynski, L. (1920): Sur le calcul du degre de continentalisme et son application dans la climatologie. In: Geografiska Annaler 2, p. 324-331.