The above map gives the approximate range for the average daily insolation values at various latitudes (averaged for the year), based on data published by NASA. These figures do not represent the summer and winter values but the best and worst places at that latitude averaged over the year.

The amount of insolation at any one point on the earth will depend on the Latitude, the season (winter or summer) and the local climate.
Around the equator, insolation figures are likely to be similar throughout the year.
At plus or minus 20^o Latitude, winter insolation figures are likely to be around 65% of summer values. At plus or minus 40^o Latitude, winter insolation figures are likely to be less than 50% of summer values.
At plus or minus 60^o Latitude, winter insolation figures are likely to be less than 10% of summer values.