A number of thoughts:
1) We've been told that Madrigal/Darby was invited to the Con about a year previous, so whoever is hatching these plans, started around the events of Dead Beat (possibly even before? Need to look at the exact dates).
2) Mab winks at Harry. To me this implies that Mab was orchestrating at least some of the events. Note also the famous PG WoJ:
Ask yourself why Mab had Molly brought in. What chain of events did that set in motion? What secondary effects came about because of it?
Jim may well be lying or misleading us, but the straight reading of that sentence implies that the actual kidnapping of Molly was Mab's idea.
3) As mentioned above, extreme heat may also be caused by Mab being busy with healing Lea. Other alternative -- seasons. Assume that Mab isn't capable of physically raising the global temperature around the world and that instead she "cheats" -- e.g. blows cold weather from the North Pole to Chicago (e.g. to help Harry during SmF). If this is the case, it makes some weird sense that "nature" would push back, creating a heat wave once Mab was done "pushing".
4) The big issue with TTHarry (and yes, I am a believer in that theory) is that it introduces a whole new complexity to the narrative. I think it would be interesting to assume TTHarry for PG, and then use Occam's Razor on everything else -- i.e. try to come up with the simplest narrative that includes TTH.
5) On the plus side, I find it interesting that Titania actually helps Harry with saving Molly. Granting him the title of "Esquire of the Summer Court" might have been a two-edged sword, but it certainly helped his credibility in the short term. I'm not sure that action really fits our image of a completely vindictive Titania.
6) Another Titania-shaped piece is that we've seen how Mab is required to fulfill Lea's debts while she was being "detained". You'd think the same thing would apply to Titania/Lily. Was Titania preventing Lily from helping Harry in the hopes of getting Lily debt to Harry to fall on Titania? The fact that Harry got around the geas by giving to Charity might not have been Titania's original plan.