date aggregation for average temperatures from 2 different tables
Instead of doing a UNION how about just doing a JOIN on them?

SET @odd:='2018-10-28';  SET @doo:='2018-11-03';

SELECT D1, T1_01, T1_02, T1_03, T1_04, T1_05, T2_01, T2_02, T2_03, T2_04, T2_05
FROM
( SELECT  
    DATE_FORMAT(T1.temp_data_dodania, '%Y-%m-%d') as D1,
    ROUND(avg(T1.temp_t1), 1) as T01_01, 
    ROUND(avg(T1.temp_t2), 1) as T01_02, 
    ROUND(avg(T1.temp_t3), 1) as T01_03, 
    ROUND(avg(T1.temp_t4), 1) as T01_04, 
    ROUND(avg(T1.temp_t5), 1) as T01_05, 
FROM temp.temp1 T1 
WHERE T1.temp_data_dodania 
   BETWEEN @odd AND @doo 
GROUP BY D1 ) A

JOIN

( SELECT  
    DATE_FORMAT(T2.temp_data_dodania,'%Y-%m-%d') as D2,
    ROUND(avg(T2.temp_t1), 1) AS T2_01,
    ROUND(avg(T2.temp_t2), 1) AS T2_02, 
    ROUND(avg(T2.temp_t3), 1) AS T2_03,
    ROUND(avg(T2.temp_t4), 1) AS T2_04, 
    ROUND(avg(T2.temp_t5), 1) AS T2_05
 FROM temp.temp2 T2 
WHERE T2.temp_data_dodania 
   BETWEEN @odd AND @doo 
GROUP BY D2 ) B
ON A.D1 = B.D2;