Here is a fact sheet about  growing pumpkins:

https://extension.colostate.edu/docs/pubs/garden/07609.pdf


And about growing plants from seed:

http://extension.colostate.edu/topic-areas/yard-garden/growing-plants-from-seed-7-409/

When planting seedlings, pay particular attention to the last frost dates and soil temperatures. 

Thank you for your question,

-Jill Bradburn
Boulder County Master Gardener

Here is additional information about frost dates and soil temperatures:
http://planttalk.colostate.edu/topics/soils-amendments-composting/1626-soil-temperatures-frosts-planting-dates/