time to set up moth lamp for Cecropia Moth?

Each year is going to be a little different, depending on the weather. I think you want to look for night time lows in the mid 50's or
better.
Here in Oregon, I go for Saturniidae around the end of May, through mid June. Each species has a different flight time, there are some
small moths that fly all year here, and I know someone who catches Prosperpina? in March, sometimes late Feb.
Just from purchased stock from the east USA, I've noticed that species that pupate below ground emerge much later, like mid-summer.
Our latitude is halfway between the north pole and the equator where I live.

The first to arrive last year after erecting the light in mid April was Luna. They began to arrive the last week of April. As for Cecropia not coming to the light, maybe that's why I never saw any last year. There was at least one species, and I don't know which one it was, that would fly up to the light, but turn and head away as fast as it came. This happened several times. It definitely wasn't Luna, but one of the darker moths.

I have posted many times on this site of my collecting of "Cold Weather/ Winter moths. Noctuidae and Erebidae. These moths are active whenever the air temperature is above 50°F. I collect them in Bait Traps, Light Traps, lifting bark and painting bait on trees and walking the bait line during the night. These moths, both Noctuidae and Erebidae are active all winter on warm nights. I may add that these moths, Noctuidae and Erebidae are dull Gray, Black and Brown and are typically overlooked by most Lepidopterists.

I will travel to Killdeer Plains WA Today to check my Bait Traps.

I will also add that I have never collected or found a Cecropia or Promethia at UV or MV light or in a light trap. I have taken males only of Callisamia angulifera at Lights.

And this little tid bit is for anyone who lives near I-71 in northern Ohio, I saw numerous cocoons of either Promethea or Angulifera between MM-80 and MM-85 on I-71 on the south bound (West side) of the interstate. Also, the Waffle House at the London, Kentucky exit several fresh Luna moths both on the ground and on the walls, especially on the back of the building. And no, I did not collect a single specimen.

I have not made an attempt to find/collect Cecropia cocoons.

I visited a site were I collected numerous Cecropia cocoons as a teenager and when I was first married. I have a drawer full of specimens. As a young boy the streets of my neighborhood had tree Lawns. Silver Maple Trees were the most common. Walking the neighbourhood I could always find Cecropia Cocoons in the Silver Mayple trees. There was also the occasional polyphemus.

There was an industrial site with lots of Silver Maple Trees and, cocoons.

Found childhood memories.