Even in temperate climates, the cold winter climate can really impact the growth of your plants. The affects all stages of growth, however, it has the biggest impact on plants during germination.
The best ways to boost your seeds chances of germinating are;
Keep them warm- seeds are less likely to germinate if they are subject to very cold, or even just fluctuating temperatures.
Keep them humid - if the air is too dry your seeds will be reluctant to start the germination process so make sure they're well watered in and somewhere with a little humidity.
Plant accordingly - not all plants like the winter, so make sure you check your seed packages for planting information before purchase. Sometimes it may be easier to grow something seasonal which will thrive without effort!