Weather

The different weather conditions have diffent effects on the match:

Bright sunshine causes a very good attendance (number of spectators). On the other hand your players will exhausting faster.
Therefore a especially good fitness of your players is in demand. A fully roofed stadium might be a helping factor for your players.
Cloudiness or scattered clouds are comfortable for your players and also a good weather condition for good attendance.
Fog causes poor sight, therefore it is not very popular for fans.
Rain will reduce the attendance and increases the lawn damage slighty.
Roofed sectors help to increase the attendance.
Heavy rain and no stadium roof are bad condtions for spectators. Only hardcore fans will come to follow those matches. The attendance is heavily decreased by this kind of weather conditions.
Furthermore the lawn will be badly effected by heavy rain. A fully roofed stadium will mitigate the negative effects on the attendance and the lawn damage.
Whilst winter weather the danger of injury increases for the players.
Even the spectators do not like much to feel very cold. A fully roofed stadium will mitigate negative effects.

Therefore the weather has a strong influence on the attendance and your income.