Watch your barometric pressure, this is key. If it is dropping, even in a pouring down rain, coyotes, foxes, and bobcats are on the move. I can not stress this enough.
It is the HUMAN that has trouble hunting in the rain, not the predators. If it is raining, barometric pressure dropping along with the time approaching for a major feeding period, you should HUNT!
We have killed them when it was raining so hard you could hardly see out of the windshield with the wipers going full blast. Barometric pressure was falling fast.
One thing that we found that was VERY necessary was to find rain suit that did not have a scratchy sound as the fabric moved against it's self. Coyotes can hear that scratchy sound for 50-75 yards.
We were nuts about watching the weather channel and would jump on the phone calling trying to find someone to hunt the leading edge and low pressure front, nail in the major and minor feeding periods, and plan to be in a favorite spot at such and such a time.
We had beater guns for this king of hunting. Some guys carried old double barrels, or best was old beater mossburg 500's that looked like heck, beat to crap, purchased at a pawn shop. The Hastings .660 choke patterns very tight in the mossburg 500. We had painted these shotguns with Krylon to protect the exterior of the shotgun, and would push a wool mop down the bore and clean out chamber when we got home. We put a finger rubber over the muzzle to keep the rain out.
What we learned that did present a major issue was wet ammo collecting dirt and grime(your pants pocket), then the shells would go in the chamber and rust up the chamber. We learned to carry a shot gun cleaning kit and break them down on the way home and clean the bore and chamber riding down the road(camper shell on the back of the truck). I had an old beater Ruger 77 sporter in 22/250 that I used, shot 1-1 1/2" groups, good enough.
The main issue we had in the rain hunting in the dessert was mud.
If you want to kill a lot of coyotes, live by the barometric pressure rising/falling along with Major and Minor feeding periods. Hard core predator hunters live by the weather and moon phase(major and minor feeding periods). If you study and chart Major and Minor feeding pattern, you will be shocked at what you find on various moon phases. This will be hard to accept, but trust it, constantly adapt your hunting habits, your hunting success will change dramatically.
I have preached this for 30 years as taught to me by one of the greats in coyote hunting who started in the late 50's, no one ever listens....even the guys that saw me turning in a lot of tails at the club meetings. I had a barometer in my house, one in the truck, and now you can get them on your I phone.
I was one of the few guys that hand called. One issue of hunting in the rain is that the air is so dense that the sound does not travel far, so you have to get closer to them or make more frequent stands. I had a hand call that seemed to be magic in the rain, the sound carried a long ways, coarse, gravely sound called the Tally Ho. This call did not sound like anything. My hunting partners nick named it the Wacker! When nothing else worked, the Wacker seemed to pull in a coyote, and used it a lot when we had to hunt in high pressure fronts. I believe that this call sounds like a deer or goat to a coyote, but I don't know...it just works. Two other hands calls that were magic was the Weems Du-tone and the Lohman(cierce) MVP-3, all very coarse sounding calls if you blew them right.
I will be buried with one of these around my neck in the coffin: http://www.ebay.com/itm/Flambeau-Lohman-Circe-Professional-3-n-1-Call-/231864694814?hash=item35fc36781e:g:sDYAAOSwstxVIUiz
Electronic calls should not be used in hard rain, but hand calls are good to go. The reeds may get clogged up, so carry an extra in your pocket. I don't know how many times I have seen a coyote fall down or slip as he tries to get some traction in the mud, reminded me of the Road runner cartoon.
Hunting in the rain, have a plan, work the plan, the plan is Barometric pressure/Major/Minor feeding periods, and right after the rain, for a very short time usually because the barometric pressure MAYBE starting to rise, which means that their smelling ability is starting to diminish.
