Time Frame

• Squash seeds are very sensitive to cold temperatures. Wait until at least two weeks after the last expected frost to plant them. Black mulch applied two or three weeks prior to planting helps warm up the soil and hastens germination.
  
  

Soil Temperature

• Plant squash when the temperature of the soil is at least 65 degrees Fahrenheit but preferably 70 degrees, the Cornell University department of horticulture advises. Squash seeds germinate best when temperatures are above 95 degrees Fahrenheit.
  
  

Considerations

• Winter squash require a longer growing period than summer squash. Plant them by mid-June---or choose fast-maturing varieties if sowing later---to give them time to ripen before autumn frosts.