Interesting, I actually interpret the climates of the two locations as different enough that they may be having important effects.
Bear in mind that the temperatures shown are averages over each entire month of 30 or so days. Averages can "hide" quite large differences in daily maximums and minimums. For example, the average high in June is 80F versus 75F. A five degree difference in averages may be reflected in substantially larger differences in daily highs. It also may be reflected in longer sequences of extreme high temperatures for any month. I expect that temperatures during critical periods of development for each bud are important for a plant that has the ability to be polymerous or otherwise different. Those critical periods may only last a few days - we do not know.
how long does it take for buds to actually form and grow before blooming, do you know? Just wondering... since the recent blooms were quite unsatisfactory, but we had 4 consecutive days in mid-July in the low 40s. Could a cold streak show up in the blooms weeks later? (Has anyone ever found a link between weather when a bud starts vs. poly blooms or aberrations in the flowers when the blooms are showing? Any studies or data?) But again - my blooms for the most part on Entwined in the Vine were not 'true' polys ... not by AHS definition, as Larry quoted. Just deformed.
There has been a little research on the development of flowering in daylilies but I do not think it is going to be helpful. The speed at which plants grow and develop depends very strongly on the temperatures they experience. It also depends on how they are grown, such as fertilizer and water. However, it also depends on all the other simultaneous demands on the plants. If a plant is producing an increase fan that may slow its development of scapes and flower buds. If it is producing seeds that may slow its development of flower buds.
Research has shown that the next scape starts to develop within a couple of weeks after the last flower is finished in
Hemerocallis lilioasphodelus But that was under the researcher's growing conditions. We do not know if they let the plants set pods or if so how many pods were set, etc. Another researcher found their timings of other cultivars to be slower and considerably variable between plants. Again, we do not have complete details on the researcher's growing conditions.
A cold streak could have an effect on flowers that open much later. It may depend on the timing. Were there unusually low temperatures or unusually high temperatures at a critical point in the development of a flower bud. We won't know because we do not know enough about bud development in daylilies. I suspect that unusually high temperatures may be a worse problem than low temperatures. Temperatures below the optimums for the development of plant characteristics may slow them down but temperatures above the optimums can damage the developing plant parts.
Your blooms may not have been structurally polymerous but that may be what we should expect when there are problems that affect the developing flower buds. 'Julie Newmar' [pollen parent of 'Entwined in the Vine'] can have polymerous blooms, for example, in Pakistan. It may be that high temperatures at a critical time during bud development produces symmetrical extra flower parts while lower temperatures causes deformed flower parts. We don't have any information.
When thinking about the development of flowers we have to remember that most likely all daylilies can rebloom but they only do so when provided with the necessary growing conditions and enough growing time. However that means that the timing of the development of scapes, flower buds, flower parts, etc. can vary enormously between locations and growing conditions where the same cultivar may only flower once a growing season and other locations where that cultivar may flower two, three or more times in the growing season. Or the timings may vary in the same location but between different years in which a cultivar does not rebloom and in which it reblooms once.
