Hard starting in warmer weather around 45-50° or higher

I have a 2000 Chevy s10 4.3l . Seems to startup and run good when cold weather but gets hard to start when weather warms up around 45-50° F or so. After getting started and warms up it seems to run on until it sets overnight then same thing occurs. But don't have this problem if it gets around 30°or cooler
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