Hi Rob,
Enabling or disabling a “warm day afternoon program” has to be done manually or you have to use the OS API Interface for this purpose.
One possibility for temperature control might be to use the IFTTT Webhooks feature to send corresponding API commands to OS. IFTTT interfaces for Private Weather Stations (PWS) like Netatmo or weather services like Weather Underground (WU) allow for triggers like temperature rises above or drops below x °C.
Please have a look at discussions like Enable/Disable Program and look at other examples given in this forum for IFTTT applets.
Hope to be some help.
Regards
Franz