Cooler weather choke issue

[DShoop7572@aol.com]

    My TR4a runs good when engine reaches what appears to be about an 1/8 
inch from red line on temp gauge. Now that the weather is much colder, the 
temp never gets to that point and I am continually adjusting choke knob. What 
is the solution to this????? 
Why does the car run smooth at a hot temp???? 

                                    Thanks
                                    Dave