the 4L60E transmission is PROGRAMMED to hard-shift in cold weather so the fluid warms up faster....

 General Motors vehicles with the 4L60E transmission are programmed with a "cold mode" that alters shifting patterns until the engine coolant reaches a certain temperature (around 133°F or 56°C). This is designed to help the engine and transmission fluid warm up faster. During this period, you may notice: 

• Delayed shifts, particularly the 2-3 shift, which might occur at higher speeds/RPMs than usual.
• Harder or rougher shifts until the fluid warms up and its viscosity decreases to an optimal level. 

These symptoms typically disappear once the transmission reaches its normal operating temperature of approximately 175-225°F (80-107°C).