Do this for each track with the Ryder database editor (thanks Ryder!)
<dynamic_environment_settings>
<clear_state_ratio>0.4601133</clear_state_ratio>
<dry_time>900</dry_time>
<heavy_rain_state_ratio>0.04786399</heavy_rain_state_ratio> lower this value or set to '0'
<ID>13</ID>
<light_cloud_state_ratio>0.2300567</light_cloud_state_ratio>
<light_rain_state_ratio>0.03190933</light_rain_state_ratio> lower this value or set to '0'
<max_humidity>0.96</max_humidity>
<max_state_duration>60</max_state_duration>
<max_temp>31</max_temp>
<max_transition_duration>60</max_transition_duration>
<max_wind_speed>4.388889</max_wind_speed>
<min_humidity>0.46</min_humidity>
<min_state_duration>20</min_state_duration>
<min_temp>17</min_temp>
<min_transition_duration>15</min_transition_duration>
<min_wind_speed>0.3888889</min_wind_speed>
<overcast_state_ratio>0.2300567</overcast_state_ratio>
<soak_time>600</soak_time>
<track>83</track> Check under 'track' This is Monza
All red values must add up to '1'. example: 0.46 - 0.0 - 0.23 - 0.0 - 0.23 adds up to 0.92 so change clear_state_ratio to 0.54 so you'll have no rain.
If you just want less rain it is trail and error with the light and heavy rain values
<dynamic_environment_settings>
<clear_state_ratio>0.4601133</clear_state_ratio>
<dry_time>900</dry_time>
<heavy_rain_state_ratio>0.04786399</heavy_rain_state_ratio> lower this value or set to '0'
<ID>13</ID>
<light_cloud_state_ratio>0.2300567</light_cloud_state_ratio>
<light_rain_state_ratio>0.03190933</light_rain_state_ratio> lower this value or set to '0'
<max_humidity>0.96</max_humidity>
<max_state_duration>60</max_state_duration>
<max_temp>31</max_temp>
<max_transition_duration>60</max_transition_duration>
<max_wind_speed>4.388889</max_wind_speed>
<min_humidity>0.46</min_humidity>
<min_state_duration>20</min_state_duration>
<min_temp>17</min_temp>
<min_transition_duration>15</min_transition_duration>
<min_wind_speed>0.3888889</min_wind_speed>
<overcast_state_ratio>0.2300567</overcast_state_ratio>
<soak_time>600</soak_time>
<track>83</track> Check under 'track' This is Monza
All red values must add up to '1'. example: 0.46 - 0.0 - 0.23 - 0.0 - 0.23 adds up to 0.92 so change clear_state_ratio to 0.54 so you'll have no rain.
If you just want less rain it is trail and error with the light and heavy rain values