Different densities react differently to added heat, and the variable that defines that difference is specific heat. Specific heat is defined as the amount of energy it takes to raise the temperatures of something one degree Celsius as it relates to mass. This value is a constant and will be the same for the same material. The equation for this is seen below:
Q = c m ΔT
Q = heat added
c = specific heat
m = mass
T = (change in) temperature
How does this relate to weather? Focus in on Lake Ontario. Water’s specific heat is 1 calorie/gram °C = 4.186 joules/gram °C. That is higher than any other common material. It takes significantly more energy to warm water 1°C than it does to warm, for example a pile of dirt or concrete. This is why there is very little change in temperature of Lake Ontario from day-to-day versus the land.
Note that in spring, the Lake Ontario water temperatures lag significantly behind in warming compared to the warming trend inland. The differences lead to robust lake breezes, especially on sunny days when there is a rapid warming of land, something the water on Lake Ontario simply cannot do because of the high specific heat. The same happens in fall when Lake Ontario has finally had enough time to warm, the land starts to trend cooler. As colder air continues to stretch southward, Lake Ontario remains warm and this results in lake-effect.
Note the lag in temperatures of Lake Ontario versus Rochester. (Data taken from http://scacis.rcc-acis.org/) Rochester bottoms out in late January and peaks in the middle of July. Lake Ontario bottoms out in mid-February and peaks in the middle of August. That delay is because of the difference in specific heat of land versus water. This difference has impacts in weather all around the world including global currents, sea and land breezes, ocean-effect rain and/or snow, and convective systems to name a few.
This is also what keeps those along the lake shore cooler for the first part of spring. North of Ridge Road/Route 104 is a common marker for this effect. The lake’s lingering warmth in fall can be linked to a stretch of lingering warmth for those that live on the lake as well.
EXTRA: Specific heat is very important in science and chemistry when it comes to certain applications like cooking. A pan will heat up quickly if it is made up of a material that has a low specific heat capacity, like aluminum. If the handle is made of plastic that has a higher specific heat, that will take longer to warm up and prevent from accidental burning.
Water is often used as a cooling agent in engines since it takes so much energy to warm. This is the case for internal combustion engines found in cars as well as nuclear reactors for power generation.