Another little known setting is the weather mask.  Use this setting to set, limit or restrict the weather conditions that drivers can use in your track.

Access the weather mask feature by selecting Special / Weather Mask from the main menu.
 

This will bring up the Weather Mask box with the following default values:
 

Now, this is fairly self-evident, but a few words anyway.

Checked boxes indicate that that weather condition is allowed.  Unchecking prevents mtmers from selecting that weather.  The option will still appear in MTM2, but it will not work.  Generally, I think it's best to let the players decide for themselves how they want to play the game, but there are a few exceptions to the rule.

The most famous example of a weather mask, of course, is Graveyard which only allows rain.  It is hard to imagine, for me anyway, racing Graveyard in any other weather condition.  To do this for your track you would simply uncheck all boxes except rain.

Another example is Misty Mountain Hop by Bowtie.  This track defaults to Dusk but can run at Night and Pitch Black.  The first thing to note here is that this would indicate that the highest check mark in the list will be the default weather condition.  It also shows that you do not have to limit your choices to only one weather selection as in Graveyard.

Lastly, you might want to use the weather mask to eliminate any weather conditions that you really don't like using.  For example, if you don't like fog, leave everything checked except fog.  Likewise for pitch black; if you don't want your friend (who's hosting) to torment you by running your track under weather conditions you despise, then take that option away.  Just uncheck the undesirable weather condition(s).  After all, it's your track, so design it to your liking.