One fact we know for sure – that sun is definitely going to set tonight.
The timing of last light is something you don't want to leave to guesswork. And just to confuse the issue, the AIP sets out a wordy definition: "Night" is that period between the end of evening civil twilight and the beginning of morning civil twilight. For all intents and purposes, first light should be construed as the beginning of civil twilight, and last light as the end of civil twilight. The terms "sunrise" and "sunset" have no relevance when calculating daylight operating times for the VFR pilot.
It's a good idea to always know when last light will occur at your destination that day, even if you plan to be on the ground well before late afternoon. You may encounter stronger than forecast headwinds, or need to make a time-consuming diversion, or even an unplanned stop which may extend your ETA significantly.
Be ultra conservative when assessing the effects of last light. The time of last light will of course change considerably with the seasons, but have a think about local weather conditions which may impact on the available light, e.g. cloud cover, and think also about the surrounding landscape. Are you flying into an airstrip that is in the shadow of a hill or mountain? In fact, there is a special note in AIP 2.7 1.2 emphasising this point:
"... the parameters used in compiling (times of Last Light) ... do not include the nature of the terrain surrounding a location, or the presence of other than a cloudless sky and unlimited visibility at that location. Consequently, the presence of cloud cover, poor visibility or high terrain to the west of an aerodrome will cause daylight to end at a time earlier than (the time stated). Allowance should be made for these factors when planning a flight having an ETA near the end of daylight."