What is the "continental effect?" How does it affect temperature?
The continental effect is a phenomenon that causes temperatures in inland areas to fluctuate more than temperatures near to large bodies of water. Large bodies of water tend to have relatively stable temperatures while large bodies of land warm up and cool down dramatically. This means that the continental effect causes temperatures to vary more greatly than they would without that effect.
Large bodies of water like oceans can store a great deal of heat without really heating up. The oceans are vast and their waters churn around, mixing together and preventing any one area from getting much hotter than any other area. This means that the temperature of the ocean does not change greatly from season to season. Therefore, maritime cities tend to have temperatures that do not change as much as inland cities.
By contrast, large areas of land cannot really keep their temperatures stable. Instead, they get very hot in the summer and very cold in the winter. They have more variation in temperature between days (when the sun heats the earth) and nights (when it does not).
The "continental effect" could also be called "the big land mass effect" because it focuses on the differences between water and land. Basically, water holds temperature better than dirt does. This means that the temperature over big hunks of land (aka continents) is going to change more dramatically than the temperature over water (which is more stable because of the water.) There are other bits involved in this, too. Obviously, the air above water is more likely to be humid and stay that way because of all that ocean, while the air above big land masses won't consistently contain the same water levels.
The gist of it is that areas being affected by the "continental effect" will have a greater range of temperatures (MDR, mean daily range) and more variety in air moisture. It may have high summer temperatures, colder nights, and even colder winters. Just think about going to the beach on a hot day in spring. The sand might burn your feet but the water stays chilly because it takes so long to warm up because of the way it holds temperature.