font-weight:200;The numbers in the google font url correspond with the style's they chose in Google Fonts. For Example:
<link href="https://fonts.googleapis.com/css?family=Crimson+Text|Montserrat|Oswald:200,300,400" rel="stylesheet">
200 is extra light
300 is light
400 is regular
Replace the number in the font-weight CSS to reflect whichever weighting you're looking to achieve.