Cloud and Wind Effects MET

Wind and cloud affect day and night temperatures in the same way, but for different reasons.

By day, increased cloud cover reflects the sun's energy back to where it came from, so not as much reaches the surface. By day, wind drags down cooler air from above, mixing it with the warm air at the surface. Both of these things make the surface air cooler, with the result that the maximum temperature during daytime will be lower with increased cloud cover or increased wind.

By night, cloud cover will absorb and re-radiate terrestrial radiation (radiation from the earth) back to where it came from. This is not exactly the same thing as reflecting it, but it has the same effect of sending the energy back to where it came from. By night, wind will drag down the (now warmer) air in higher levels. Both of these effects mean the surface air will not get as cold as it otherwise would have done. So the minimum temperature overnight will be higher with increased cloud cover or increased wind.

For the mathematically inclined, if you imagine the temperature over a full day as being a sine wave, then either increased cloud or increased wind will result in a "flatter" sine wave, with a lower high and higher low.