What affects radar signals?

[partsfreak]

There are a few local false signals that I pass everyday to use as a benchmark for my RD's. I have noticed that in the morning the range of detection is greater than the afternoon with the only vaiables I have noticed are:
Morning its darker and generally colder.
Traffic volume is about the same at both times.
weekends when traffic is lighter the detection is up slightly but still follows morning/afternoon patterns.
The difference in range is about 150yds.
Anyone have any idea what the cause of this variance could be?

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[Cips]

Weather, humidity, of course different things to reflect from; just to name a few. I hope more experienced people chime in here.

[crisptito]

My V1 today seemed extra sensitive. The known K and X signals were detected further away than usual and I was getting both sides of the door sensors on the bogey counter from further away. Only difference is that today was very cold, no humidity at all and very low dewpoints. Agree with Cips that weather makes a big difference.