In Palestine there is commonly hardly any rain from the early showers of spring to October. Hence, "rain in harvest" became sometimes (see the marginal reference) a supernatural sign, sometimes, as here, a proverb for whatever was strange and incongruous.

As snow in summer - None of these is suitable to the time; and at this unsuitable time, both are unwelcome: so a fool to be in honor is unbecoming.

As snow in summer, and as rain in harvest,.... Which were very undesirable and unseasonable, yea, very hurtful to the fruits of the earth; and a great obstruction to the labourers in the harvest, and a hinderance to the gathering of it in; and were very rare and uncommon in Judea; it was even a miracle for thunder and rain to be in wheat harvest, 1-Samuel 12:17;
so honour is not seemly for a fool: for a wicked man; such should not be favoured by kings, and set in high places of honour and trust; "folly set in great dignity", or foolish and bad men set in honourable places, are as unsuitable and inconvenient as snow and rain in summer and harvest, and should be as rare as they; and they are as hurtful and pernicious, since they discourage virtue and encourage vice, and hinder the prosperity of the commonwealth; such vile persons are contemned in the eyes of good men, and are disregarded of God; he will not give, theft, glory here nor hereafter; the wise shall inherit it, but shame shall be the promotion of fools, Proverbs 3:35; see Ecclesiastes 10:6.

Honour is out of season to those unworthy and unfit for it.

(Proverbs. 26:1-28)
The incongruities of nature illustrate also those of the moral world. The fool's unworthiness is also implied (Proverbs 17:7; Proverbs 19:10).

There now follows a group of eleven proverbs of the fool; only the first of the group has after it a proverb of different contents, but of similar form:
As snow in summer, and rain in harvest;
So honour befitteth not a fool.
If there is snow in high summer (קיץ, to be glowing hot), it is contrary to nature; and if there is rain in harvest, it is (according to the alternations of the weather in Palestine) contrary to what is usually the case, and is a hindrance to the ingathering of the fruits of the field. Even so a fool and respect, or a place of honour, are incongruous things; honour will only injure him (as according to Proverbs 19:10, luxury); he will make unjust use of it, and draw false conclusions from it; it will strengthen him in his folly, and only increase it. נאוה (= נאוי) is the adj. to the Pil. נאוה, Psalm 93:5 (plur. נאווּ); נאוה, Proverbs 19:10, and נאוה, Proverbs 17:7, are also masc. and fem. of the adj., according to which, that which is said under Proverbs 19:10 is to be corrected. Symmachus and Theodotion have translated οὐκ ἔπρεψεν, and have therefore read נאוה. The root word is נאה (as שׁחה to שׁחוה) = נוה, to aim at something (vid., Hupfeld under Psalm 23:2).