Summer bloom uses an unused day heat value

Meaning its intended values don't match with the actual day phase temperature.

In worldtemperature.lua:

local SUMMER_BLOOM_TEMP_MODIFIER = 0.10 / TUNING.DAY_HEAT   -- amount that the daily temp. variation factors into the overall bloom

TUNING.DAY_HEAT is unused in Don't Starve Together, phase temperature for the day is set using this private table a bit above it, so it should be using that value.

local PHASE_TEMPERATURES =
{
    day = 5,
    night = -6,
}

Although, if SUMMER_BLOOM_TEMP_MODIFIER is intended to use a higher value than the phase temperature in DST, it should probably be clarified and be manually defined there.

Also, this table could be changed to reference those tuning variables instead (and have the values changed to 5 and -6):

local PHASE_TEMPERATURES =
{
    day = TUNING.DAY_HEAT,
    night = TUNING.NIGHT_COLD,
}

And yes, while world temperature isn't synced between server and clients, doing this would make it easier to change with all_clients_require_mod mods, without having to do upvalue hacking and/or replacing the functions entirely.