Average Temperature Outlook for CLE ELUM (issued in September 2017) suggests that during Oct-Nov-Dec 2017:

There is a 99% chance that the average 3-month temperature will be within the range of 30.1 and 42.5 Deg F,.

There is a greater ( 52.0%) chance that the temperature will be higher than the climatological median* of 36.3 Deg F, and a lesser (48.0%) chance that the temperature will be lower than the climatological median*.

*For the climatological reference information, the median statistic is reported. The median value means that during the present climatological reference period (1981-2010), half of the years (50%) temperature was greater than the median and in the other half (50%) less than that.