Xiao Ming is a "little guardian of environmental protection". After class, he often cares about the changes in the environment and weather.

The fluctuation of (1) temperature is relative to the previous day, so it can be assumed that the average temperature of last Sunday is a variable X, so the average temperature of Sunday should be X+(1.1-0.3+0.2+0.4+1.. This gives x= 13.4. The temperature from Monday to Sunday this week is:

Monday: x+1.1=14.5

Tuesday: x+1.1-0.3 =14.2.

Wednesday: x+1.1-0.3+0.2 =14.4.

Thursday: x+1.1-0.3+0.2+0.4 =14.8.

Friday: x+1.1-0.3+0.2+0.4+1=15.8.

Saturday: x+1.1-0.3+0.2+0.4+1+1.4 =17.2.

Sunday: 16.9

The highest is the average temperature on Saturday, 17.2℃.

(2) The average temperature is (14.5+14.2+14.4+14.8+15.8+17.2+16.

(3) The local average temperature data has changed greatly, and this year is close to the highest level in the same period in history, far higher than the lowest level in history.