Is there ANY Add-on equipment that can be purchased to improve signal reception during heavy cloud cover?

Not really.  The best approach is an optimally aligned satellite dish to minimize the effects of rain fade.  

Please post back with your signal readings for each satellite's transponders (and both tuners if applicable).  You'll find these readings under "Menu" -> "Setup" -> "System Setup" -> Satellite -> "View Signal Strength".  Note the "+" and "-" symbols next to the "Satellite" and "Tuner" entries where you can toggle the readings between the various satellites and both DVR tuners. 

Fill in your readings for each satellite and tuner using these examples.  A properly aligned dish will show 80-90s on most of the relevant transponders (although some will be low or zero):

Satellite transponders (32 total at 101º)

[Most of your standard definition channels are beamed from 101ºW]

1-8    #   #   #   #   #   #   #   #

9-16   #   #   #   #   #   #   #   #

17-24  #   #   #   #   #   #   #   #

25-32  #   #   #   #   #   #   #   #

Satellite transponders (3 total at 110º)

[Not present with Slimline3 dish. No channels are currently beamed from this satellite]

1-8    NA  NA  NA  NA  NA  NA  NA  #

9-16   NA  #   NA  #   NA  NA  NA  NA

Satellite transponders (11 total at 119º)

[Not present with Slimline 3 dish. Local SD channels for some cities, Spanish package]

17-24  NA  NA  NA  NA  NA  #   #   #

25-32  #   #   #   #   #   #   #   #

Satellite transponders (16 total at 99º(s)) [or 99º(b)]

[Local HD channels for some cities]

1-8    #   #   #   #   #   #   NA  NA

9-16   NA  NA  NA  NA  NA  NA  #   #

17-24  #   #   #   #   #   #   #   #

[Note: these can be very slow to appear]

Satellite transponders (14 total at 99º(c)) [or 99º(a)]

[National HD channels]

1-8    #   #   #   #   #   #   #   #

9-16   #   #   #   #   #   #   NA  NA

[Note, these can be very slow to appear]

Satellite transponders (16 total at 103º(s)) [or 103º(a)]

[Local HD channels for some cities]

1-8    #   #   #   #   #   #   NA  NA

9-16   NA  NA  NA  NA  NA  NA  #   #

17-24  #   #   #   #   #   #   #   #

[Note, these can be very slow to appear]

Satellite transponders (16 total at 103º(ca))

[National HD channels beamed from D12 satellite]

1-8    NA  NA  NA  NA  NA  NA  NA  NA

9-16   #   #   #   #   #   #   #   #

17-24  #   #   #   #   #   #   #   #

Satellite transponders (14 total at 103º(cb)) [or 103º(b)]

[National HD channels beamed from D10 satellite]

1-8    #   #   #   #   #   #   #   #

9-16   #   #   #   #   #   #   NA  NA

17-24  NA  NA  NA  NA  NA  NA  NA  NA

Satellite transponders (9 total at SWM)

[You'll only see this if you have a Single Wire Multiswitch (SWM) dish]

1-8    #   #   #   #   #   #   #   #

9-16   #   NA  NA  NA  NA  NA  NA  NA

I THINK MY DATA LOOKS GOOD, BUT JUST HEAVY CLOUD COVERAGE WILL DROP MY SIGNAL. MEANING IT DOESN'T HAVE TO BE A THUDERSTORM OR EVEN RAINING AT TIMES.

rjl19939,

Don't touch that dish!!!!!!! You definitely have a spot on alignment with those signal strength readings!! I am surprised you get very much signal loss at all, regardless of the weather.

Yeah, those readings are great. You must get some VERY heavy cloud cover!

Are you sure there's not an active volcano nearby just south of you and those clouds are ash instead of clouds:0)

Not many volcanoes to the southwest of Baltimore, but those big, dense black clouds often associated with a Chesapeake Bay line squall can hold a lot of water.  Radio waves don't transmit through water very well.  That's just physics and there's nothing that can be done about it.

Thanks for the input. I actually live on the ocean in Delaware. They asked for the closes city. We do get a lot of storms, but I lose signal in lite rains and cloud cover. This weekend. I lost signal at 10 am. Irene was still in Hatteras and we weren't having any  rain yet, just overcast skies.  I don't know what to do. Love the product but you can't live on the Ocean and not have weather and news. 

Thanks again for the help.

Take a look outside in the vicinity of the dish when this is happening to see if there's anything odd going on.  I'm thinking of such things as vegetation that wind might be blowing into the signal path or water running off a roof over the antenna.

rjl19939,

Sure hope Irene spared you any problems!!!! I was fortunate that my wife and I returned to Tennessee on 8/14 after a week and a half staying in Rodanthe, NC at the Outer Banks in our travel trailer. Last year the week before Labor day we had to outrun the inclement weather produced by Hurricane Earl when we went on vacation to Bar Harbor, Maine. It's beautiful on the East Coast, but like you said...you gotta watch the weather closely this time of the year.

Perhaps moisture is getting into one of the exterior coax cable connectors?

Yep,  that was my next thought too.  If there's nothing odd going on outside, check signal levels again when you're actually having a problem.  Pay particular attention to the 99 and 103.  If its a connector problem as litzdog suggests, it will show up there first.