[1] The terrain around Koromilia is flat to the southwest, but to the northeast it is hilly.

[a] The highest point in the vicinity is 373 meters above sea level, 1.1 km east of the Koromilia.

[b] Around Koromilia it is sparsely populated, with 10 inhabitants per square kilometre.

[4] The nearest major community is Kilkis, 9.4 km south of Koromilia.

The warmest month is July, when the average temperature is 28 °C, and the coldest is December, with 2 °C.