How can I counter Fungal Growth + Blinding Cloud as Terran?

HoTS introduced new units that force all races to have a higher variety of spellcasters on the field.

Versus Infestor-Viper you'll need Siege Tanks and Vikings of course, just as before. But since Fungal Growth and Blinding Cloud can be very obnoxious, Ghosts are now a must versus that composition IMHO.

Ghosts can EMP which removes 100 energy from a unit. If the Infestor wasn't at full energy, he most likely won't have enough for Fungal; if the Viper wasn't at full energy, he won't have enough for Blind Cloud. Snipe from a cloaked Ghost is also a pretty good counter to Infestors and Vipers.

Then it's all about positioning; if your army is out of position, he might be able to drop the combo. If he moves his spellcasters out of position, you will be able to incapacitate them.

PS: Fungal Growth is now a projectile. I haven't tried it, but the Raven's PDD should intercept the missile. Does PDD works versus Abduct too?

And Seeker Missile, since it's an ability, should not be affected by Blinding Cloud. Since they do 125 damage on impact, 3 or 4 of these in a clump of Infestors will kill most of them.

The same trick has always worked against Infestors, and it is no different in Heart of the Swarm: space em out.

Your marines should never clump up when you know there are Infestors on the field. Clumping makes it so easy to melt those marines with a fungal. Instead, space out your marines and keep them spaced out and converge on the infestors in a half-arc or phalanx formation.

By spacing our your marines, significantly fewer marines will be hit by fungal and conversely, they won't be hit by blinding cloud either. Remember, with units like Marines its not about keeping individual units alive, but inflicting more damage to your opponent than you take yourself. If he burns all his fungals and clouds on killing 10 marines, killing his 10 Infestors in return with your remaining marines is a very cost effective strategy.

Tanks work the same way.

The best strategy for tanks has been to space them out so that each tank can assist another tank that is getting hit with melee attackers. The range on cloud is quite small and can usually only hit one tank at a time if they are spaced out. If a melee unit gets in the face of a tank, another tank can assist - even if vulnerable tank is under a cloud. A tank is cheaper than a viper - so you should have more tanks than he has vipers.