What changed? Are you using a different flour? Are the eggs the same size as they always were? Do you cook the noodles as long as before? Are you rolling the pasta as thin as you used to or are you slacking off, but cooking thicker noodles for the same amount of time? Any of these variables could affect your current crop of noodles – if a new brand of flour has more protein, if smaller eggs are trying to bind the same amount of flour, and if the cooking time is not adequate, or not adequate for thicker noodles, yours could be coming out tough.
If nothing has changed, however, you’re probably adding a bit more flour than necessary. The flour needs to be correct in proportion to the egg. In her seminal work Essentials of Classic Italian Cooking (Canada, UK), Marcella Hazan recommends 1 cup of unbleached all-purpose flour for every 2 large eggs. You may need to vary that up or down, depending on the eggs’ ability to absorb the flour. But try to be conservative. It is possible that the increased humidity in your kitchen that comes with warmer weather is coaxing you to add more flour to compensate for extra moisture in the dough. Fight the urge to add flour, and try to keep your dough a little bit on the sticky side rather than dry.