do Cities at the same latitude receive same amount of insolation?

Question

and how would lack of atmospheric moisture cause a great annual temperature range

Answer 1

If you mean solar isolation then yes, they will have similar isolation unless they are located in a major geographical formation. Such as a steep sided mountain valley.

On your second question. Water has a great ability to retain latent heat. And that changes how the atmosphere reacts. It acts kind of like a wool blanket. When it is cold it keeps the air really cold, if it is warm then it stays warm even when the heat sources is gone.

Answer 2

Latitude is only one of the factors in considering a region's annual temperature range, as well as amount of moisture received.

However, when looking at the amount of atmospheric moisture, ranges will be more narrow the higher the average moisture content. This is because the moisture itself helps to keep the temperature at a constant rate. Thats not to say that it will hold the temperature steady, but it will help to resist the temperature changes, which narrows your range.

The other part to atmospheric moisture is the relative distance to a large body of water. If you look at what regions have higher moisture contents, they are areas in which there are large bodies of water. Oceans and very large lakes are the primary sources. With these, the water in the lake/ocean is much harder to change than that of the air around them. As a result, you will see that the temperature will fight between the atmosphere/weather, and the temp of the water. This furthers the resistance to temperature changes, and decreases the range even further.

For an example of how this works, compare the temps between San Fransisco and LA. The water coming in to SF is much much colder than that of LA. As a result, the average temp in SF is ~10-15 degrees colder than that of LA.

You can do a local experiment on this as well. On a warm day, go down near a pond. You'll notice that the temperature drops. If you were to go near that same pond on a cool day, you would feel that the temperature is either warmer or about the same as the air, depending on how cold the water and air are.

Answer 3

Atmosperic moisture in itself isn't the cause of great annual temperature change. What matters, is how far away from the ocean the city is.

On the west coast of North America, where the ocean is relatively warm and the weather systems flow west to east. The ocean warms the cities on the coast and to some degree , hundreds of miles inland
So the winters are milder than in the center of North America where winters get real cold.
The summers on the west coast are cooled by the influence of the ocean, whereas the Center of North America do not get cooled, and so have hotter weather.

So it is closeness to oceans that matter and to warm oceans even more so. The North Altlantic is a lot colder, so the moderating effect in Winter is less