Depends upon the angle subtended from the sun between where you are and the perpendicular. More acute, greater the heat. This heat has a bearing on plant growth but some confusion will again enter. Density, pollution, moisture, etc will modify what I wrote above. The angle may be more acute at the Equator then Dallas but the atmospheric layer at the Equator is higher, more dense, more polluted(more population cooking on wood) and more moist. Hence cooler.
Regards,
Arif.
