The contour maps of Costa Rica below for each month of the year show the average High, Average and Low Temperature in °F fore every region of the country color coded by the legend at the bottom of each.
There are a number of other weather map resources on Costa Rica Guide including a series like this for rainfall and cloud cover (or sunniness as we’d rather think of it) each month of the year for each region, an action packed little map that pops up a chart of rainfall for each month when you mouseover any region and another that does the same for temperatures.
A long article with lots of diagrams explains the basics of how weather works in Costa Rica, a live map of today’s weather, current storms, and there are even instructions to make your own accurate weather forecast.
If this is all WAY more than you were looking for then the general weather tendencies for every month of the year are summarized on the Best Time To Visit Costa Rica page along with a calendar of sea turtle nesting, whale migrations, quetzal nesting, surf size, tides charts, holidays, fiestas and music festivals for every month of the year.
Pretty boring eh? Almost every month looks nearly the same as the month before and the month after. For the most part the temperatures don’t vary widely with the seasons in Costa Rica. As far as temperatures are concerned you can pretty much ignore when you’ll be in Costa Rica and just pay attention to where you’ll be. Of course higher elevations are cooler.