If the sun is closest to earth on midsummer day, 21st June, why is it usually warmer in July and August?

Answer 1

First, it's not that the earth is closest to the sun on June 21st.

The earth is tilted on its axis. On June 21st, it's getting the most direct sunlight over a longer period of time.

It continues to get warmer after that because the rate at which it heats during the day is greater than the rate that it cools at night.
That decreases as the angle of the sunlight and the length of the day decreases until the net gain in energy is negative and it starts to cool.

Answer 2

Somebody asked the reverse of this question, i.e. why is the coldest time a month or so after the shortest day in winter.

So, to repeat; think of the "heat store" of an area as rather like a tank of water, with a hose running into it; on the longest day this hose runs full bore; on the shortest it runs slowly.

This tank has leaks in it, representing the heat loss from any system - radiation into space mainly in th ecase of the earth.

Now, as you increase the flow of water, representing the approach to summer and lengthening of days, you reach a point where you are putting mor ein than leaks out, so the tank level rises. This represents the increase in temperature.

After the 21st of June you begin to reduce the flow again, but the important thing is, you are still putting more in than you are losing; your tank level (or temperature) will only start to fall when your inflow is exceeded by your leaks. This will obviously be some time after the date of maximum inflow.

In winter the reverse happens; even though the flow rate starts to increase again after the shortest day, it still isn't enough to counteract the losses until some time later.

Answer 3

It's the result of some complex geometry. While 21 June is the longest day (for the Northern Hemisphere at least) the sun's maximum intensity isn't for a little while after that.

Also, (other people have mentioned this but I'll reiterate) the amount the sun's distance varies isn't enough to be noticable, summer and winter are purely the result of the angles, nothing to do with distance.

Answer 4

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I don't think the Sun is closer to the Earth in the summer, I think it's closer in mid winter. What makes it hot in the summer is the angle at which the Sun rays hit the Earth. I think it takes about 3 weeks time for the Earth to warm up, so even if the heat starts in May it may take another month before we feel it at that intensity.

The tilt of the earths axis is responsible.

Answer 5

It's not closest it’s longer than other days. The directness of the sun is more hot then than other days because it is right above you in the summer and it is colder in the winter because the sun is low in the sky all day which it does not get much heat which makes it colder. But the reason why it gets warmer a month or two later is because high pressure builds and all the weather action move up north because the weather pattern changes at this time of the year.

The best way I can explain in words why it is hotter in the summer in a short time is look a a world globe and you will notice that it is tilted t on side. If you hold the Earth in place and move the frame of the globe 1/2 a turn you will see the earth go up or down. When the Earth is on the other side of the sun this is what happens:
Look here to see what I mean:
This is For America and other places in the Northern Hemisphere:
http://csep10.phys.utk.edu/astr161/lect/time/seasons.gif

This is for places in the Southern Hemisphere like South America and Australia ( you will notice the season are completely opposite of what ours are):
http://csep10.phys.utk.edu/astr161/lect/time/seasons-south.gif

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There is a popular misconception that the seasons on the Earth are caused by varying distances of the Earth from the Sun on its elliptical orbit. This is not correct. One way to see that this reasoning may be in error is to note that the seasons are out of phase in the Northern and Southern hemispheres: when it is Summer in the North it is Winter in the South.
Seasons in the Northern Hemisphere
The primary cause of the seasons is the 23.5 degree of the Earth's rotation axis with respect to the plane of the ecliptic, as illustrated in the adjacent image (Source). This means that as the Earth goes around its orbit the Northern hemisphere is at various times oriented more toward and more away from the Sun, and likewise for the Southern hemisphere, as illustrated in the following figure.

http://csep10.phys.utk.edu/astr161/lect/time/seasons.gif

The Seasons in the Northern Hemisphere

Thus, we experience Summer in the Northern Hemisphere when the Earth is on that part of its orbit where the N. Hemisphere is oriented more toward the Sun and therefore the Sun rises higher in the sky and is above the horizon longer, and the rays of the Sun strike the ground more directly. Likewise, in the N. Hemisphere Winter the hemisphere is oriented away from the Sun, the Sun only rises low in the sky, is above the horizon for a shorter period, and the rays of the Sun strike the ground more obliquely.

In fact, as the diagram indicates, the Earth is actually closer to the Sun in the N. Hemisphere Winter than in the Summer (as usual, we greatly exaggerate the eccentricity of the elliptical orbit in this diagram). The Earth is at its closest approach to the Sun (perihelion) on about January 4 of each year, which is the dead of the N. Hemisphere Winter. (The time for perihelion, aphelion, and the solstices for any year 1992-2000 is available in this compilation.)

For a more extensive introduction to how variations in the amount of solar energy reaching the Earth's surface influence climate, see this discussion of solar databases for global change models.
Another Fallacy to Avoid
Incidentally, one should be precise in terminology. A common student answer for the cause of the seasons is that "the Earth tips toward the Sun in the Summer, . . .". This conveys the impression that the Earth moves around its orbit and at certain times of the year the rotation axis suddenly tips one way or another and thus we have seasons. As the preceding diagram makes clear, the rotation axis of the Earth remains pointed in the same direction (except for small effects from precession) as it moves around its orbit. It is the relative location of the Sun with respect to this constant tilt angle that causes the seasons, not some elaborate square dance of the Earth bowing to its partner as it moves around its orbit!
Southern Hemisphere Seasons
As is clear from the preceding diagram, the seasons in the Southern Hemisphere are determined from the same reasoning, except that they are out of phase with the N. Hemisphere seasons because when the N. Hemisphere is oriented toward the Sun the S. Hemisphere is oriented away, and vice versa:

http://csep10.phys.utk.edu/astr161/lect/time/seasons-south.gif

The Lag of the Seasons
The preceding reasoning for the causes of the seasons is idealized. In reality, we know that the seasons "lag": for example, the hottest temperatures in the Summer usually occur a month or so after the time of maximum insolation (the time when maximum solar energy is deposited during a day at a point on the surface of the Earth). This is because the Earth and its atmosphere store heat (the oceans are particularly effective heat sinks). Thus, a detailed description of the seasons is quite complicated since it must take into account complex local variations in the storage of solar energy. However, the basic reason for the seasons is simple, as described above.

http://csep10.phys.utk.edu/astr161/lect/time/seasons.html

Answer 6

It is only mid summers day in the northern hemisphere. The distance between the earth and the sun and the effect of the sun on the seasons is more complicated. See attached link.

Answer 7

I don't think the Sun is closer to the Earth in the summer, I think it's closer in the winter. What makes it hot in the summer is the angle at which the Sun rays hit the Earth. I think it takes some time for the Earth to warm up, so even if the hottest starts in May it may take another month before we feel the heat at that intensity. I might be wrong...sorry...

Answer 8

The sun is closest on JANUARY 4th and furthest on JULY 4th.
The tilt of the earth's axis has more effect on the climate. You would expect the seasons to be more extreme however south of the equator but more sea is in the south which makes the climate stable

Answer 9

You are assuming the longest day is when the sun is closer to the earth
Remember the orbit around the sun is an elipse and therefore that will affect the heat.
I know, I am talking a lot of rubbish but I don't get out much and this makes me happy

Answer 10

It isn't closest to the earth, it is at its most northern part of its cycle, and in the northern hemisphere.

Why it heats up in July - August, i don't know, we need a scientist to answer that one!