Why isn't June 21 the hottest day as the longest?

Answer 1

For the same reason that it's not hottest at noon: temperature lags heat input. The earth doesn't come to equilibrium on the day with the highest heat input; the next day the sun is still putting enough heat into the system to make it a little warmer. And the next day and so on until the heat input drops enough that it's not quite enough to make things continue to get hotter, then the temperature starts to drop. The higher the heat capacity, the greater the lag. Oceans can store a lot more heat than land. Places that are dominated by oceans (like the west coast of North America) are not only more moderate, the annual high comes later than in places that are far from oceans. The the highest average daily high Omaha is in mid-July, three weeks after the solstice. In Seattle it's the first week of August, three weeks later.

Answer 2

Many factors go into the weather, not just how close the northern hemisphere is to the sun on the 21st of June. With so many other factors, the weather can vary from area to area and year to year. Usually the hottest days in the northern hemisphere are actually after the 21st of June, as it takes a while for the heating up process to peak. So July and August are often hotter than April and May. In winter it is the same, with the coldest weather usually being after the 21st of December.

Answer 3

The hottest day typically occurs a few weeks after the summer solstice (June 21) because it takes time for the Earth to warm up. The oceans, land, and atmosphere need time to heat up from the increased solar radiation received during the longer days around the solstice. This delayed response means that temperatures continue to rise even after the days start getting shorter.

Answer 4

It takes time for the land to heat up.