This mod from ilurker gives you options to remove night, add sunshafts to most weather, and change the frequency weather types occur.
ilurker's Additional Sunshafts and Weather Pack
v1.0 - 9/20/08 - 1.5.04 - English
I put together this mod to tweak some of the weather settings and to add sunshafts to some weather types. These work for all areas, but have only been significantly tested in Cordon.
Please send any bug reports, comments, or suggestions to firstname.lastname@example.org.
Replace fsgame.ltx with the one provided in the zip.
Copy the gamedata folders for the mods you want into the root of the Clear Sky directory, overwriting files as prompted. This mod should have no conflicts with anything that does not alter weather effects.
All mods in the frequency folder are 100% compatable with mods in the effects folder. The Sunshaft Clouds mods will work with any of the storm mods.
You'll need to wait for the weather to transition for the mods to take effect, so don't expect them to kick in right on load.
Description of Mods
These mods add a sunshaft effect to lightning, giving the illumination a strong directional aspect and making it somewhat blinding if you look right into it.
This mod sets all weather effects for each type to their noon version. Weather will still transition as normal and the time of day will advance, but the sun and lighting will stay at 12:00.
This mod removes night, and replaces it with an extended twilight from 20:00 to 5:00. Weather will still transition, but I have not taken the time to properly calculate the sun position to make it seem like a true extended dusk, so dawn has a pretty abrupt transition in shadow orientation.
This mod replaces normal, drizzly rain with full on thunderstorms. Has three sunshaft options.
These mods add sunshafts to cloudy weather in various intensities, resulting in a soft, diffuse glow. Has three intensity options.
Eliminates cloudy, rainy, and stormy weather altogether.
Creates a 24/7 thunder storm in the zone.
Replaces all clear weather with cloudy weather. Storms and rain will remain the same.