Spring ( March) and Autumn ( October) Equinox and Relationships with satellites (source Wikipedia)

An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator
One effect of equinoctial periods is the temporary disruption of communications satellites. For all geostationary satellites, there are a few days/weeks around the equinox when the sun goes directly behind the satellite relative to Earth (i.e. within the beam-width of the groundstation antenna) for a short period each day. The Sun's immense power and broad radiation spectrum overload the Earth station's reception circuits with noise and, depending on antenna size and other factors, temporarily disrupt or degrade the circuit. The duration of those effects varies but can range from a few minutes to over an hour.
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In Laymans terms,  The immense radiation from the sun since it is directly behind the satellites during these periods, it is focussed  on the centre of our receiving dishes, this radiation is not just light frequencies but a mass of others and a lot within the frequency range of the LNBs of the satellite dish and is seen as electrical noise. This causes the LNB's to overload, causing loss of amplificaation of the genuine Satellite frequencies, hence derterioration of the already low signals for your TV system.
Whilst we are on the subject another reason for loss of quality signals here on the Costa Blanca.
Your system looks at several satellites at 28.2 º East called Astra, some are northern beams and some are southern. Most of the  Free to Air TV channels are on Astra 2D which is a northern beam and  has a very weak and scattered coverage on the Costa Blanca, some signals are less than 10 watts (hence the dish szes) in the UK these signals average 50 watts.
To get these signals  especially for single cable community system we need a very large dish, a 2.4m dish has an average
gain of  47 dB and the LNB  a gain of 50 dB. We need this high gain to try to get the low level signals.
However, there is a problem and that is... at 28,5 º East we have a another satellite called Eurobird 1 and this is a European beam. It has an  average output power of  50 watts which is 5 x the signal power of Astra 2D ( Costa Blanca).
It is not difficult to see that whilst we are trying to get las "last drop" of signal from Astra 2D, the signal from Eurobird 1 is    " over the top" for our high gain equipment causing the LNB to be saturated  and subsequent deterioration of the alraedy weak signals.
We have to remember that English TV  from Astra 2 D is intended for UK use only, that is why it is broadly focussed to Northern Europe and not Spain, due to late 90's technology ( that's when the Satellite was constructed) the beam is not tightly focussed and some of it's footpring covers parts of Spain albeit  much weaker. Loss of signal quality is something we all have to accept.