I think hot weather alters firms' desire to sell at some given price because hot weather increases the demand for ice cream. (Mankiw's book) I am reading &quot;Principles of Economics&quot; by N. Gregory Mankiw.
I think hot weather alters firms' desire to sell at some given price because hot weather increases the demand for ice cream.
Am I wrong?

Notice that when hot
weather increases the demand for ice cream and drives up the price, the quantity
of ice cream that firms supply rises, even though the supply curve remains the
same. In this case, economists say there has been an increase in “quantity supplied”
but no change in “supply.”
Supply refers to the position of the supply curve, whereas the quantity supplied
refers to the amount producers wish to sell. In this example, supply does not
change because the weather does not alter firms’ desire to sell at any given price.
Instead, the hot weather alters consumers’ desire to buy at any given price and
thereby shifts the demand curve to the right. The increase in demand causes the
equilibrium price to rise. When the price rises, the quantity supplied rises. This
increase in quantity supplied is represented by the movement along the supply
curve.
Yes, you are wrong. As the quoted part explains,

In this case, economists say there has been an increase in “quantity supplied” but no change in “supply.” Supply refers to the position of the supply curve, whereas the quantity supplied refers to the amount producers wish to sell.

Are you willing to sell your current computer for say \$1 000? What is the lowest price that you are willing to sell for? (Just a ballpark estimate will do.)
If you came up with a number, you did that without knowing anything about the prospective buyers of your computer.
Of course it is very nice to be able to sell for more, if the customers are - for some reason - willing to paying more, but the ability to do this is determined by the equilibrium. The supply curve merely describes the vendors' preferences. What is the lowest price at which they are willing to sell / what quantity are they willing to sell if the price turns out to be X.