Planting too early or in cold soil can lead to poor germination or crop failure. Purdue Extension warns that crops like cucumbers and peppers, which are very tender, may not survive frost or cold soil conditions. Similarly, cabbage-family crops and onion sets planted too early may bolt, reducing their yield. Gardeners in frost-prone areas or low-lying regions should be particularly cautious, as temperatures can vary significantly within short distances. Using soil thermometers and frost protection measures, such as row covers, can mitigate these risks.