there is/are

Neither "standing water" nor "temperate climate" are pluralized, so "is" is used before them.

there is standing water and a temperate climate

This sentence is rather non-sensical. Do you have a bigger context to put it in?

CalifJimthere is standing water and a temperate climate

This sentence is rather non-sensical. Do you have a bigger context to put it in?

I agree that the sentence is awkward. Perhaps composition would require the two elements to be less closely connected.

this sentence comes from Toefl tests,this is the original sentence:

find the mistake in the sentence below:

3.Mosquitoes are [easily] [found] wherever there is [standing] water and [temperate] climate.
A.easily
B.found
C.standing
D.temperate

and the answer is ' a temperate climate'.

teachers,I still don't understand why it's 'there is' i

Standing water + a temperate climate is the condition required for breeding in this case. These two are taken together as inseparable and so, singular.

Like, bread and butter is good for........