Recovery at sea level in high heat and humidity is slow and tough, even in comparison to altitude training. I have done both extensively. A given pace feels very easy when you go from Florida to the north in the fall or spring. The altitude-like effect is in the increase in red blood cells, which is accomplished in heat by an increase in blood volume overall, as an adaptation to the constant loss of fluids and hence, the need to maintain more fluids, in contrast to altitude where you have an adaptation that increases the concentration of red blood cells. I had a series of pr's when I was at altitude, and then they continued at sea level for nine months after that. When I had good training partners at sea level with heat and humidity, the pr's and pr shape resumed for several years--and most of those new pr's were set in relatively easy times of day or periods of the year in Florida where I might well have run much faster up north.