Hairy question - transpose columns

Hello;
I've got pluviometric data in a bizarre format (spanish administration is rather original) and I need to "transpose"
them,to be able to use them as time series data for a model.
 
The original data are in a format like
cod_var |  Year  |  Month  |  Ten  | RainDay1 | RainDay2 | RainDay3 | Rainday4 | Rainday5 | RainDay6 | RainDay7 |
RainDay8| Rainday9 | Rainday10 | Rainday11
 

--------------+-----------+------------+---------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
   452   | 1995   |  1          |   1     |       2         |     5          |     6           |      -3         |
0        |        5        |        4       |      5         |      4          |     4          |             452   |
1995  |  3          |    2    |       4         |     5          |     0           |       5         |      3         |
     23       |        4       |      34       |      4          |     2          |             452   | 1996   |  12
   |    3    |      12        |     2          |     3           |       4         |      7         |        3        |
      3       |      15       |      2          |     4          |        3     452   | 1998   |  9          |    2
|      2         |     8          |     6           |      -3         |      5         |        0        |        2
 |      6         |      0          |     1          |             452   | 1998   |  3          |    3    |       2
   |    -3          |     7           |       9         |      4         |        2        |        5       |      6
    |      1          |     16        |        3
 
......................

As you may see, the date of a rain datum is defined by the value of the fields Year, Month,Ten (1=first ten days of
month;2=second ten days of month; 3=up to eleven last days of month).
 
and the field in which the datum is (RainDay1, RainDay2...)

This is no useful for me because I need something like:
cod_var |  Year  |  Month  |  Day  |      Rain     | 
--------------+-----------+------------+---------+----------------+--     452   | 1995   |  1          |   1     |
2         |        452   | 1995   |  1          |   2     |       5         |                 452   | 1995   |  1
  |   3     |       6         |         452   | 1995   |  1          |   4     |      -3         |        452   | 1995
|  1          |   5     |       0         |                 452   | 1995   |  1          |   6     |       5         |

...................

Perhaps this is not possible to do with a database? Should I manage to make a program to fix this?

Thanks for your help. I really can't imagine how to do this with Postresql; though I'm a newbye.

Regards
-----------
Javier