Final answer:
In New York City and Beijing, the highest insolation occurs in July due to the effects of seasonal lag following the summer solstice, where increased direct sunlight and longer daylight hours contribute to warmer temperatures.
Step-by-step explanation:
The month with the highest insolation in New York City and Beijing, both located in the Northern Hemisphere, is July. Although the highest position of the Sun and longest day occurs during the summer solstice around June 21, the hottest months tend to be July and August. This delay is due to the Earth's bodies of water, like oceans, which require time to heat up - a phenomenon known as seasonal lag. The process of absorbing and then releasing heat from the water means that even after the summer solstice, the temperature continues to rise, leading to higher insolation in July.
Beijing follows a pattern similar to New York City due to its location in the Northern Hemisphere, where insolation peaks in July when the effects of seasonal lag cause temperatures to be the highest post-solstice. During summer, the Earth's tilt towards the Sun in the Northern Hemisphere not only means more direct rays but also longer daylight hours that further contribute to the increase in insolation.