Why are spring evenings cold?			In May, in northern countries, when the sun is shining, the day is warm but the nights are cold. Later in the summer, evenings are warmer. There is more difference between day and night in the spring, less in the summer. Why? Because heat comes in two ways, by radiation and convection. Radiation is when the sun shines and makes you warm. Convection is when the air around you is warm. In the spring, you get more heat by radiation from the sun, but only when the sun shines. In the evenings, when the sun is low, you feel the cold of the air.
					May: More heat from the sun.	Autumn: More heat from the ground.