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Friday night I'll be playing with trumpets and trombones outside in low 20s degree weather. I expect the pitch to really move around every time the instruments change temperature. If you have any insights about how fast the pitch drops on one horn vs. another, let me know please.

If you are curious to see how it works out, come Aurora IL.

unfortunately, large instruments, tubas, euphoniums etc. go down in pitch faster that smaller brass instruments. Conn did a pamphlet authored by their chief acoustician in the 1950s or '60s that addresses this. In total, you do have to push your slide in as the trumpets will go flat less. It's even more of a problem when woodwinds are present. Tusabtuba

I am in the same camp as the posts about relative pitch. The third answer about the rate and degree of drop is my first concern. We are going to rotate in and out of doors alternating with recorded music, so we'll be changing up and down several times. This will be my first rodeo with such a situation. And we have an alto sax with us just to stir the pot.

In normal weather I try to get a little on the low side of the pitch. Tomorrow will be like that song "Free-fallin'".

Here's the debriefing:
Weather was high 20s. I pushed in a little before we started. I told the bloke's story about how long the slide is on the trumpet, etc. Everything sounded fine and we never spoke about it once we started. The alto sax seemed well in tune with the rest, but she's masterful at adjusting, so there you are. Thanks for the advice.

bloke wrote: if there IS any slide-pulling, let the trumpets pull DOWN to YOU.

This is good advice. We do this in my Army band regardless of the group. Tune to the horn that can adjust the least. As long as you are all together that's all that matters.